Groupprops:Error log

Did you find something that looks like an error (or possible error) to you? Report the error quickly here (anonymous, does not require login, but you can optionally provide an email ID to be notified of the fix).

See below for some errors that have been caught and fixed in the past.

As we try to make Groupprops more reliable, this log is intended to keep a record of errors that satisfy either of these two criteria:

• The error was on a highly trafficked page (more than 1000 cumulative pageviews so far) and stayed online for at least 24 hours.
• The error stayed online for at least a month.

The log was started in 2011. This page lists the errors fixed in 2012 and later. The log of errors fixed in 2011 is at Groupprops:Error log/2011.

Note that the page does not list spelling and formatting errors if those errors do not affect the mathematical or factual meaning of the content. The page does list major formatting errors on high traffic pages that create trouble with displaying or understanding part of the text.

Factual errors in high traffic pages

These include glaring factual errors of commission or omission.

Page	Error description	Version where it was introduced	Version where it was corrected	Why error? Why not caught? ("I" refers to Vipul)
Element structure of symmetric group:S3	It said "Since 2 - 1 = 1 and 2 + 1 = 3 are powers of 2" which is wrong.		July 6, 2022	relatively obscure location within a large page
Direct product of group of rational numbers and group of rational numbers modulo integers	It said $\mathbb{Q} *_{\mathbb{Z}} \mathbb{Z}$ instead of $\mathbb{Q} *_{\mathbb{Z}} \mathbb{Q}$	March 1, 2013	December 27, 2021
Nilpotent group	One of the shorthands didn't correspond to details, and the verbal statement was incomplete.		December 26, 2021	carelessness
Octahedral group is isomorphic to S4	I didn't have the word "orientation-preserving"		December 26, 2021	The fact probably wasn't in my mind clearly enough.
Linear representation theory of symmetric group:S3	Far down in the page, it said characteristic 2 at one place where it should say characteristic 3. Information earlier in the page was correct.		December 5, 2021	Probably a copy-paste error that didn't get caught because it was far down in the page
SmallGroup(16,3)	One of the generators was described as $x$ in the presentation but as $c$ later in the page.		June 15, 2021
Symmetric group:S4	Missed out on an endomorphism that's equivalent as a homomorphism but not as an endomorphism to one of the existing endomorphisms already listed		January 26, 2020
General linear group over a field	Order of $GL(2,5)$ incorrectly stated as 240 instead of 480		July 6, 2019
Groups of order 16	Error in permutation representation of SmallGroup(16,3)	April 15, 2017	July 6, 2019
Projective special linear group	Wrote wrong prime factorization of 360		July 6, 2019	Not a primary reference point, so didn't read/review carefully
Fraction of tuples satisfying groupy relation in subgroup is at least as much as in whole group	Used $\cap$ instead of $\times$ at a few places in the formula		July 6, 2019	Long proof, typos while writing it out
Dihedral group	Missed the case $n = 6$ for rational group		July 6, 2019	Probably a misconception at the time of page creation; never went back and corrected it even after realizing that this isn't true
Element structure of projective special linear group of degree two over a finite field	The order of Jordan blocks of size two was stated to be $q$ and should in fact be $p$		July 5, 2019	Mentally thinking of $p$ and $q$ as the same based on typical cases
Series-equivalent not implies automorphic	Smallest example was stated as being of order $2^7$ but in fact it's possible to construct an example of order $2^6$; actually, the construction used in the example can be pruned by removing a redundant direct factor	August 22, 2009	July 5, 2019 (further correction)	For some reason, there was a belief that there are no examples of order 2^6, so this led to motivated cognition.
Order formulas for linear groups	Fourth row of table used projective general linear group instead of projective special linear group		November 24, 2017	carelessness
Monster group	Exponent of 13 in order was stated as 1 instead of 3		November 24, 2017	carelessness
Splitting-simple group	Definition of simple group in one of the tables said every proper nontrivial subgroup is normal; it should have said no proper nontrivial subgroup is normal		November 24, 2017	carelessness
SmallGroup(16,3)	A quotient group was incorrectly stated to be elementary abelian group:E8 instead of dihedral group:D8		November 24, 2017
Index satisfies intersection inequality	Had $H:K$ instead of $G:K$	October 16, 2008	August 28, 2017	carelessness; did not proofread
2-Sylow subgroup is TI implies it is normal or there is exactly one conjugacy class of involutions	Incomplete sentence		August 12, 2017	Proofreading error
Odd-order cyclic group equals derived subgroup of holomorph	missed "holomorph of" in section "Breakdown at the prime two"	December 1, 2008	July 1, 2017
Locally cyclic group, directly indecomposable group, splitting-simple group	incorrectly stated that locally cyclic implies directly indecomposable and implies splitting-simple	April 11, 2017 (one of the edits)	July 1, 2017 (multiple edits)	Genuine confusion; was thinking of the prime power order case and didn't think clearly about the case of multiple primes
Normal p-complement	Stated that Hall's theorem says normal p-complements must always exist for solvable groups; but it only talks of p-complements (not normal ones)		July 1, 2017	Carelessness; page created before processes in place to check facts
Associative implies generalized associative	Missed special case of second part of product being single letter	July 31, 2008	June 22, 2017	Edge case that I missed
Locally finite group	Version with symbols for definition 3 did not include injectivity clause mentioned in verbal version.	April 15, 2017	May 11, 2017	copy-paste error
Groups of order 18	direct product of S3 and Z3 was marked as not metacyclic, though it is	September 17, 2009	February 18, 2017	carelessness
2-Sylow subgroup of special linear group:SL(2,5)	The subgroup was wrong. Four of the elements were not even in SL(2,5).	June 28, 2011	October 26, 2016	carelessness, this edit was made a long time ago before proper procedures were in place for error detection
Nilpotent group	Had a duplicate row on torsion-free nilpotent group, with one of the duplicates giving incorrect information		September 9, 2016	carelessness or misconceptions at the time of addition of the incorrect row
Element structure of special linear group:SL(2,5)	One place in a table had a factor of 2 in one description that shouldn't have been there		August 13, 2016	carelessness
Finite and any two maximal subgroups intersect trivially implies not simple non-abelian	The description of Step (2) referenced Step (3) whereas it should have been Step (1 )		June 20, 2016	Error only in expandable box that's collapsed by default, and not in proof logic itself.
Zassenhaus isomorphism theorem	Incorrect statement of one of the terms in the theorem, wrote $C \cap D$ instead of $B \cap C$		May 30, 2016	careless, also did not revisit the page to review
subgroup structure of groups of order 24	Incorrectly stated number of 2-subgroups for groups of IDs (24, 6) and (24, 7)		February 22, 2016	line copy off-by-one error
index is multiplicative	roles of subgroups $H, K$ were interchanged in part of the proof		November 15, 2015	change in notation midway through article creation process
element structure of symmetric group:S3 and (by inclusion) symmetric group:S3	in table, indicated that the 3-cycle conjugacy class does not split in the alternating group in S3.		August 29, 2015	carelessness, insufficient review of table contents
automorphism group of alternating group:A6	wrote that the automorphism group of the alternating group of degree three is the symmetric group, but actually it's the cyclic group of order two.		June 7, 2015	carelessness, forgot that $A_3$ being abelian introduces complications.
Coxeter group	for symmetric group and direct product, stated that some entries are 0 when they're actually 2; also a typo in one of the matrices with an entry marked as 3 when it should be 2.		May 15, 2015	insufficient attention to detail in a complex page on a topic I didn't have a lot of prior knowledge of.
simple non-abelian group	Forgot to say "normal" when invoking the definition of simple group		May 15, 2015	carelessness, insufficient page review
normal subgroup	The summary description of the second isomorphism theorem in the Isomorphism theorems section stated the condition as "$N$ is contained in the normalizer of $H$" rather than "$H$ is contained in the normalizer of $N$."		November 10, 2014	carelessness, insufficient proofreading
groups of order 81	somewhere on the page, incorrectly listed the groups with IDs 9 and 10 as having nilpotency class 2 instead of 3, though the correct value had been listed above		June 8, 2014 (here and here)	Carelessness, reasons for slip unclear
automorphism group of a group	wrote the automorphism group of cyclic group:Z8 as cyclic group:Z4 instead of Klein four-group		February 25, 2014	didn't review the page carefully
element structure of projective general linear group of degree two over a finite field	One of the multiplied-out formulas for the total number of elements was wrong, though the factored form was correct (missed a factor of $q$ in the multiplication)		February 3, 2014	Only cross-checked the answer in factored form.
subgroup structure of alternating group:A6 (error also propagated via inclusion in alternating group:A6	wrote one of the generators as $(1,2,3,4)$ rather than as $(1,2,3,4)(5,6)$.		December 31, 2013	careless analogy with twisted S3 in A5
element structure of alternating group:A4	In the section element structure of alternating group:A4#Multiple ways of describing permutations, had listed $(1,4)$ as a permutation in the group.		November 18, 2013	carelessness, didn't check long list.
a template error on the template page Template:Subgroups dissatisfying property sorted by importance rank resulted in some incorrect examples being displayed for central factor (although the incorrect template was also used on the normal subgroup page, no incorrect examples were displayed there as a result).		January 19, 2013	February 16, 2013	the error was in a very limited subset of the examples generated, and not in the most prominent examples, so it escaped notice.
alternating group	incorrect description of exponent for the case of odd $n$	August 27, 2009	February 1, 2013	carelessness; the right formula was used on other pages such as the page on alternating group:A5.
special linear group:SL(2,3)	mistakenly stated that every automorphism of GL(2,3) is inner		January 20, 2013
central factor	In one of the equivalent formulations of the definition, forgot to state the precondition of normality necessary for the rest of the definition to make sense		January 19, 2013
characteristicity is transitive	In the "Given" of the "Hands-on proof" wrote that $H$ is characteristic in $G$ instead of $H$ being characteristic in $K$	October 20, 2008	June 27, 2012	didn't check carefully
linear representation theory of symmetric group:S3	didn't state the size of the conjugacy class of the 2-transposition in the character table column header	July 16, 2011	June 3, 2012	copy-paste error when shuffling columns
symmetric group:S3	In one of the explanations, stated that the group is an ambivalent group, but the observation that needed to be made was that the group is a rational group.	June 29, 2011	May 31, 2012
group	for the "minimum number of variables needed to describe condition" column, I had "2" instead of "1" for inverse element.	February 25, 2011	May 5, 2012	didn't review/revist page often enough
symmetric group:S7	error in the code link for "similar groups"		April 28, 2012	error not directly visible on page, only upon clicking link
groups of order 16	had $(1^5)$ instead of $(1^4)$ as the Hall-Senior symbol for elementary abelian group:E16		April 17, 2012	minor error on long page
alternating group:A6	forgot factor of half in order formula for PSL(2,q)		March 19, 2012
special linear group:SL(2,3)	forgot to include whole group in list of normal subgroups		February 29, 2012, also changing the format of the page	minor
symmetric group:S4	used formula $q^2 + 1$ instead of $q^2 + q - 1$ for number of conjugacy classes in $GA(2,q)$		February 22, 2012	genuine misconception, got cleared when creating the page for element structure of general affine group of degree two over a finite field
linear representation theory of symmetric group:S4	mistakenly stated in the section on orthogonality relations and numerical checks that there are no abelian normal subgroups		February 20, 2012	far down in page

Other errors in high traffic pages

These include formatting and display errors, as well as minor errors of omission.

Page	Error description	Version where it was introduced	Version where it was corrected	Why error? Why not caught? ("I" refers to Vipul)
Fully invariant subgroup	Typo: wrote "group" instead of "subgroup"		August 18, 2021
Left coset space of centralizer is in bijective correspondence with conjugacy class	Typo: wrote $g$ instead of $x$		July 6, 2019	Oversight, insufficient review
Subgroup structure of direct product of D8 and Z2	Column alignment issue in table		July 6, 2019	Data correct in source, missing syntax easy to miss without carefully looking at output table
Normal subgroup equals kernel of homomorphism	Missed a closing paren		July 6, 2019	Minor omission
Cyclic maximal subgroup of dihedral group:D8	Typo: $a^x$ instead of $a^2x$		July 6, 2019	Minor typo
Determination of character table of alternating group:A5	Typo in internal link and wrong order of information (stated 2 <= a number before the explanation was provided)	February 27, 2014	March 9, 2017	reshuffling of page content during creation, and typos
subgroup structure of symmetric group:S3	Two minor issues in the Conjugacy class-defining functions section: a dangling math tag in the first row, and a missing cell in the second row causing a column alignment problem		September 23, 2016 (edit 1, edit 2)	carelessness, insufficient review
normal subgroup generated by a subset	Used $\le$ instead of $\subseteq$ in describing the containment of the subset in a subgroup		May 8, 2014	carelessness
cyclic group:Z2	wrong link, some poor grammar in an explanation for the number of conjugacy classes.	January 20, 2013
element structure of alternating group:A4	messed up some column alignments		series of edits culminating in this. Most of the errors were fixed within the 24-hour grace period for error reporting.	didn't check column alignments
element structure of symmetric group:S3	used "formula for number of conjugacy classes" in a column header instead of "formula for order" although the section header and other language made it clear this refers to a formula for the order.		November 24, 2012
finite solvable group	couple of rows with column mis-alignments		June 5, 2012
dihedral group:D8	the subgroup lattice diagram overlapped partially with the subgroup structure table	The error was likely propagated by a font size change made to an automatically included text from the subgroup structure of dihedral group:D8 page with this edit on January 8, 2012.	May 31, 2012. Also reverted the size edit on the other page	didn't realize how size changes could impact pages where the text is included, so didn't check for that.

Factual errors in low traffic pages

Page	Error description	Version where it was introduced	Version where it was corrected	Why error? Why not caught? ("I" refers to Vipul)
Transitive subgroup property	The section on transfer condition operator missed a clause that $K$ has property $p$ in $G$.		October 14 2021	carelessness
Transitive subgroup property	The row for "Disjunction-closed subgroup property" said "Yes" even though the detailed description correctly said "No".		August 18, 2021
Finite normal implies amalgam-characteristic	Confusingly, $K$ was used in place of $L$ at a few places in the proof!		August 18, 2021 (followup	Different notation was used in different edits!
Transiter master theorem for composition operator on subgroup properties	Concluding para for right transiter still used "left transiter"		August 18, 2021	Copy/paste error, carelessness
Central factor	Quantifier rank was incorrectly stated as 2 instead of 3		August 18, 2021	Maybe some genuine confusion about quantifier rank
First-order subgroup property	First-order description for central factor was a bit off, missing a clause; fixed it by changing to the simpler description that eliminated a variable		August 18, 2021 (further edit)	Oversight
Maximum degree of irreducible representation of subgroup is less than or equal to maximum degree of irreducible representation of whole group	superscript/subscript interchange for restriction		August 17, 2021, August 17, 2021	The meaning is clear from context so the error is hard to catch.
purely definable subgroup	the row for pure definability is quotient-transitive used "normal" instead of "purely definable" at one place		June 1, 2020	copy/paste error
subisomorph-containing subgroup	definition interchanged roles of $G$ and $H$		June 1, 2020	typo
subgroup structure of central product of D8 and Z4	incorrect number of occurrences of a subgroup		July 6, 2019	typo, didn't review carefully
Grigorchuk group	incorrectly stated to be 2-generated; in fact it is 3-generated but not 2-generated		July 6, 2019	insufficient understanding of the group structure
binary operation on magma determines neutral element	word "associative" where it shouldn't be, when describing a magma		July 6, 2019	page created a long time ago before quality control; insufficient review
determination of character table of alternating group:A5	sign error in one of the equations	March 15, 2017	July 6, 2019	Carelessness, also I ultimately "got the right answer" so I didn't check the steps carefully
holomorph of Z8	incomplete presentation; a relation is missing		July 6, 2019	Oversight, insufficient review
ideal class group	incorrect statement that every finite abelian group can be realized as an ideal class group; the reality is more uncertain		July 6, 2019	Really old page creation and edits; don't remember reason for confusion
element structure of symmetric group:S8	it said "partitions of the number 6" instead of "partitions of the number 8"		July 5, 2019	Minor typo, doesn't materially affect calculation
element structure of special linear group of degree three over a finite field	the expanded form of the polynomial for "Has Jordan blocks of sizes 2 and 1 with equal eigenvalues over $\mathbb{F}_q$" had $q^2$ instead of $q^3$		July 5, 2019	Relatively minor error in one expression among many
locally nilpotent not implies normalizer condition	explanation for why a subgroup is self-normalizing was incomplete and misleading	April 17, 2017	July 1, 2017	Loose analogy with a slightly different proof led me astray; also didn't think of precise differences with finite case
surjunctive group	Missed injectivity from condition	January 29, 2014	February 24, 2017	Lack of familiarity with topic of definition
finite non-nilpotent and every proper subgroup is nilpotent implies not simple	reasoning had a slight error; a statement made universally was established only existentially, and needed to be modified to intermediate strength to make the logic work.	December 20, 2011	June 19, 2016	subtlety, didn't catch
2-generated group	said "comprises two elements" instead of "comprises at most two elements" for the generating set		December 23, 2014	not thinking of edge cases
automorph-conjugacy is not finite-intersection-closed	used curly braces (set notation) instead of angled braces (subgroup generated notation) when describing the subgroup $H \cap K$		December 19, 2014
powering-invariant over quotient-powering-invariant implies powering-invariant	statement was incomplete, didn't include the conclusion to be proven from the hypothesis.		December 19, 2014
powering-invariance is not quotient-transitive	the explanation of the third bullet point in the proof ($K$ is not powering-invariant in $G$) was incorrect.		December 19, 2014
split algebraic group	original definition made it appear as if the Borel subgroup is unique and/or that the condition being true on one Borel subgroup is equivalent to it being true on any other.		May 5, 2014	genuine confusion, not enough effort to clarify the definition.
recursively presented group	stated the generating set must be finite, the more standard definition allows for countably infinite generating set	May 31, 2007	November 5, 2013	genuine confusion as to what definition is more standard
supersolvable implies nilpotent derived subgroup	Had $N_{i-1} \cap [G,G]$ rather than $[G,G]/(N_{i-1} \cap [G,G])$		October 16, 2013
compatible pair of actions	used action-on-each-other symbols $\alpha,\beta$ instead of conjugation action symbols for one of the alternate definitions		September 13, 2013	carelessness
linear representation theory of general linear group:GL(2,3)	incorrectly stated that the binary octahedral group has the same character table (the groups are isoclinic, so they have the same character degrees, but not the same character table)		September 2, 2013	either carelessness or conceptual confusion at the time of page creation
linear representation theory of general linear group:GL(2,3)	a -1 and 1 were swapped in the description of the last character		August 31, 2013	checked only a sample of entries, not all
deducing the Baker-Campbell-Hausdorff formula from associative algebra manipulation	off by constants, forgot to subtract 1 from a non-critical alternative description		August 18, 2013
Baer Lie group	stated "torsion-free" instead of "2-torsion-free" though the link was correct		August 5, 2013	minor carelessness.
algebraic group is topological group under Zariski topology (deleted page)	wrong page (entirely)		July 27, 2013	although the conceptual error was fixed a while back, this particular page didn't get deleted.
linear representation theory of groups of order 96	For groups of GAP-ID 224 and 225 (3rd column of the table), the 3 irreducible representations are of degree 4, not of degree 6.		July 9, 2013	carelessness, not enough review of table entries
groups of order 5	wrote "2 is a prime number" instead of "5 is a prime number"	April 19, 2011	May 3, 2013
groups of order 3	wrote "2 is a prime number" instead of "3 is a prime number"	April 19, 2011	May 3, 2013
Galois extensions for dihedral group:D8	said "neither $a$ nor $-a$" instead of "neither $b$ nor $-b$"		May 2, 2013
RSA algorithm	wrote "congruent to the order of the group" instead of "congruent to 1 modulo the order of the group"		May 2, 2013
group cohomology of dihedral group:D8	wrote $n = 8, 2n = 16$ instead of $n = 4, 2n = 8$	January 15, 2013	April 2, 2013	The error was due to copy/paste from group cohomology of dihedral group:D16 without appropriate modification.
Schur-trivial group	small issues of wrong words used in verbal explanations for reverse impliation falures.		February 24, 2013
characteristic not implies amalgam-characteristic	had $\times$ instead of $\rtimes$ at one intermediate step of explanation.		February 21, 2013
no nontrivial homomorphism to quotient group not implies complemented	stated example using GL(2,3) instead of the binary octahedral group.		February 16, 2013, with a redirect to No nontrivial homomorphism to quotient group not implies complemented normal	carelessness and/or confusion.
classification of finite 2-groups of maximal class	Didn't clarify the exception for $n = 3$ where the semidihedral group doesn't exist		February 8, 2013	carelessness
field generated by character values	stated that it is a cyclotomic extension of the rationals; the correct version is that it is contained in a cyclotomic extension of the rationals.	July 13, 2011	January 31, 2013	careless error
Tour:Factsheet one (beginners)	omitted the adjective "associative" in one of the definitions.	July 26, 2008	January 31, 2013
dicyclic group:Dic20	had missing relation in alternate presentation	September 17, 2009	January 15, 2013	carelessness, low priority page
ascendant subgroup and Descendant subgroup	did not specify behavior at limit ordinals, making the definition vacuously true for all subgroups in all groups	March 23, 2007 (for ascendant subgroup) and March 23, 2007 (for descendant subgroup)	December 20, 2012 (for ascendant subgroup) and December 20, 2012 (for descendant subgroup)	careless, didn't visit page often
groups of order 720	listed one of the groups as Mathieu group:M11 instead of Mathieu group:M10		December 18, 2012	carelessness
Frattini quotient	made statement for finite nilpotent group that is only valid for a finite p-group, namely that the Frattini quotient is elementary abelian		November 25, 2012	careless error
group cohomology of Klein four-group	In section "cohomology groups for trivial group action" subsection "over an abelian group" the table entry for $H^3$ read $\operatorname{Ann}^2$ instead of $\operatorname{Ann}^3$		November 22, 2012	typo
semidihedral group	had a "+1" instead of "-1" in the presentation definition	July 19, 2010	October 24, 2012	typo, didn't read carefully
topological group	incorrectly stated that algebraic groups are topological groups		July 30, 2012
characteristic not implies fully invariant in finite abelian group	wrote $\mathbb{Z}$ in place of $\mathbb{Z}/8\mathbb{Z}$ at one place		July 3, 2012	copy-paste from earlier example, didn't fix
derivation-invariance is transitive	did not state "$A$ is a derivation-invarant subring of $B$" as part of the Given in the proof section	October 8, 2008 (first revision)	June 27, 2012	didn't check carefully
skew of 2-cocycle for trivial group action of abelian group is alternating bihomomorphism	used left instead of right at one place		June 24, 2012
Tour:Inquiry problems one (beginners)	forgot to state what $\infty$ times $\infty$ is, and did not clearly state that the multiplication rules are for multiplication both ways		June 23, 2012 and more edit, last one June 25, 2012
semitopological group	had definition of quasitopological group instead, thought they mean the same thing		June 23, 2012, corrections across multiple pages
left-topological group	had interchanged roles of left and right in definition		June 23, 2012
right-associative elements of magma form submagma	Had written "left" instead of "right" in a few places in the proof of part (3) involving nil elements		June 20, 2012 (two edits)	didn't revisit page
verifying the group axioms	not really an error, but rather, an omission. Didn't check that the so-called inverse map is actually well defined from $G$ to $G$.		June 19, 2012 (final of a series of minor edits)
linear representation theory of special linear group of degree two over a finite field	wrote maximum degree of irreducible representation is $q + 1$, but this is not true for $q = 2,3$		June 17, 2012	didn't check exceptional small cases
classification of groups of order four times a prime congruent to 3 modulo 4	wrote 4 divides $p - 1$ instead of 4 divides $p - 3$, did not state $p > 3$		June 14, 2012	did not revisit page
formal group law	stated that all of $R[[t]]$ acquires a group structure, instead of the maximal ideal		June 13, 2012
normal subgroup of finite group	in (3) of the three equivalent definitions, didn't state the clause that the whole group is finite		June 6, 2012
black-box group algorithm for finding the subgroup generated by a subset	used $F,H$ in place of $F_i,H_i$ at one place		June 1, 2012	Change of notation, didn't completely verify that the change was propagated everywhere
linear representation theory of groups of order 16	a couple of sentences in the "grouping by Hall-Senior families" section referred to order 32 instead of 16, though the mathematical content wasn't affected		May 31, 2012
general affine group and related pages	mistakenly assumed that all extensions over prime subfield are Galois, used $\operatorname{Gal}(K/k)$ instead of $\operatorname{Aut}(K)$		May 31, 2012 (multiple edits on multiple pages)
element structure of special linear group of degree two over a finite field	wrote "characteristic 3" in place of "odd characteristic" at one place. While the statement was correct, it did not constitute the explanation it purported to be		May 31, 2012
Kunneth formula for group homology	Had $A$ in place of $M$ at one place		May 29, 2012	notation change, didn't fix all symbols
symmetric subset	In the definition, said the following equivalent conditions instead of both the following conditions	June 13, 2007	May 26, 2012	didn't visit page often enough
Hall not implies order-isomorphic	wrote down order of $PGL(2,23)$ in place of $PSL(2,23)$ at one place and mis-stated one of the Hall subgroups		May 21, 2012
Burnside group	interchanged roles of parameters to describing the Burnside group		May 20, 2012
first cohomology group	superscripts ${}^2$ instead of ${}^1$ at some places.		May 10, 2012	copy-paste error.
faithful irreducible representation of quaternion group	mistakenly used the word "representation" instead of "character" in the summary table		April 29, 2012	minor error, didn't review/revisit page enough
faithful irreducible representation of dihedral group:D8	did not say "of characteristic not two" at one of two places in the "Embeddings" section		April 29, 2012	minor error, didn't review/revisit page enough
symmetric group:S8	error in link code for "similar groups"		April 28, 2012	error not visible on page, need to click link or observe carefully
fusion systems for dihedral group:D8	excluded one of the possibilities for the fusion system		April 26, 2012	conceptual confusion, didn't think about this enough
element structure of special linear group of degree two over a finite discrete valuation ring	In the formula for the order of the group, the exponent on $q$ read $4l - 3$ and it should read $3l -2$	November 4, 2011	March 30, 2012	confused, didn't devote adequate thought to the computation, didn't revisit often enough
Weyl group	one of the equivalent definitions used the word "kernel" instead of the word "image"		March 30, 2012	didn't visit page frequently
imperfect group	Stated mistakenly that hypoabelian implies imperfect.	September 9, 2009	March 22, 2012	confusion about transfinite behavior
minimal splitting field need not be cyclotomic	mistakenly stated that every minimal splitting field is contained in a cyclotomic extension of the rationals. The correct version is that every finite group has a minimal splitting field that is contained in a cyclotomic extension of the rationals.		February 29, 2012	The error was introduced at a time when I was unclear about this topic, and I didn't correct it even after it became clearer.
number of irreducible representations over rationals equals number of equivalence classes under rational conjugacy	Used word "reals" instead of "rationals" at one place		February 19, 2012	Minor typo
number of irreducible representations over rationals equals number of equivalence classes under rational conjugacy	Had the false sentence "Note that the statement is not true for an arbitrary finite group.		February 19, 2012	The error arose from an earlier version of the page/statement. It didn't get fixed when transitioning to the new version.
element structure of special linear group:SL(2,5)	wrong description of eigenvalue pairs for one of the conjugacy classes		February 18, 2012	minor detail
element structure of special linear group:SL(2,5)	had "3" instead of "2" in one of the coefficients of a characteristic polynomial		February 18, 2012
element structure of special linear group of degree two over a finite field	Mistakenly stated the minimal polynomial as $(x - a)^2$ when it should have been $x - a$		two fixes, first one messed up, second one right: February 18, 2012	didn't proofread
element structure of special linear group of degree two over a finite field	Mistakenly stated the minimal polynomial as $x - a$ when it should have been $(x - a)^2$		February 18, 2012	didn't proofread
element structure of general linear group of degree two over a finite field	Mistakenly stated the minimal polynomial as $x - a$ when it should have been $(x - a)^2$		February 18, 2012	didn't proofread
non-associative ring	listed associativity as one of the compatibility conditions	March 3, 2010	February 17, 2012	carelessness, not visited page often
linear representation theory of semidihedral group:SD16	wrong column headers for two columns in the character table		February 5, 2012
upper central series may be tight with respect to nilpotency class	had a wrong example, too strong a statement		February 2 (first edit), February 2 (second edit)	carelessness
linear representation theory of M16	had $\langle a^2,x \rangle$ and $\langle a^2x \rangle$ in place of $\langle a^4,x \rangle$ at some places		January 16, 2012
groups of order 32	wrote "7" instead of "5" in explanation for why there are 7 abelian groups of order 32		January 16, 2012
linear representation theory of groups of order 32	in the section on classification up to isoclinism, the derived subgroup for $\Gamma_6$ was stated as cyclic group:Z2 when it is in fact cyclic group:Z4.		January 16, 2012	copied from groups of order 32 page that had a similar error.
groups of order 32	in the section on classification up to isoclinism, the derived subgroup for $\Gamma_6$ was stated as cyclic group:Z2 when it is in fact cyclic group:Z4.		January 16, 2012	details
extended centralizer	mistaken statement about relation between being a real element and extended centralizer equal to centralizer	July 25, 2009	January 15, 2012	did not visit page
group of Glauberman type for a prime	missed out on quantifying $P$ as a $p$-Sylow subgroup of $G$		January 14, 2012
equivalence of definitions of group of Glauberman type for a prime	missed out on quantifying $P$ as a $p$-Sylow subgroup of $G$		January 14, 2012
p-normal group	said "contains $P$" instead of "contains $Z(P)$" at a couple of places		January 14, 2012	didn't visit page
Connected topological group	Mistakenly stated that connected iff no proper open subgroup		January 12,2012	The statement is true in some contexts, e.g., for locally connected groups.

Other errors in low traffic pages

These include formatting and display errors, as well as minor errors of omission.

Page	Error description	Version where it was introduced	Version where it was corrected	Why error? Why not caught? ("I" refers to Vipul)
GA(2,2) is isomorphic to S4	An unclosed toggledisplay tag caused one of the steps of the proof to be hidden.		December 27, 2021	carelessness, visual completeness of page even with the hidden step
isomorph-containing subgroup	"weakly close" instead of "weakly closed" at one place		June 1, 2020	typo
subgroup structure of central product of D8 and Z4	Math formatting causing a table row to not show correctly		July 6, 2019
finite non-nilpotent and every proper subgroup is nilpotent implies not simple	Some key terms in the statement were missing, make it incomprehensible (specifically, because of the use of [[fact about::nilpotent group;3| ]])	December 20, 2011	June 20, 2016	error introduced after version upgrades/formatting changes later