More on exact bicoverings of 12 points

摘要

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