Zalesskii group

Definition
The Zalesskii group can be defined as the following subgroup of unitriangular matrix group:UT(3,Q). Note that the group is not unique up to isomorphism, because the choice of group depends on the choice of prime partitioning in Step (1). The number of such groups up to isomorphism equals the cardinality of the continuum.

The group was constructed by Zalesskii to demonstrate that there exist infinite nilpotent groups in which every automorphism is inner.