Quasi-symmetric designs on 56 points

Abstract

Computational techniques for the construction of quasi-symmetric block designs are explored and applied to the case with $56$ points. One new $(56,16,18)$ and many new $(56,16,6)$ designs are discovered, and non-existence of $(56,12,9)$ and $(56,20,19)$ designs with certain automorphism groups is proved. The number of known symmetric $(78,22,6)$ designs is also significantly increased.