Quasi-symmetric 2-design

This term is related to: incidence geometry
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Definition

A quasi-symmetric 2-design is a design of type $(1,2)$ with constants $l_1$ and $l_2$ such that any two blocks intersect in either $l_1$ points or $l_2$ points. For example, a Steiner triple system is a quasi-symmetric 2-design with $(l_1,l_2)=(0,1)$.

Relation with other properties

Stronger properties

• Symmetric 2-design
• Steiner triple system