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