More on Exact Bicoverings of $12$ Points

Abstract

The minimum number of incomplete blocks required to cover, exactly $A$ times, all $t$-element subsets from a set $V$ of cardinality $v$ ($v\ge t$) is denoted by $g(\lambda ,t;v)$. The value of $g(2,2;v)$ is known for $v=3,4,\dots ,11$. It was previously known that $14\le g(2,2;12)\le 16$. We prove that $g(2,2;12)\ge 15$.