%N Number of covers of an unlabeled n-set such that every point of the set is covered by exactly 4 subsets of the cover and that intersection of every 4 subsets of the cover contains at most one point.
%C Cover may include multiple occurrences of a subset. Also n-rowed binary matrices with distinct rows and all row sums 4.
%H <a href="/A058790/a058790.pdf">Formula</a>
%Y Cf. A050535, A050913, A058783-A058785.
%A _Vladeta Jovovic_, Nov 30 2000