%N Number of covers of an unlabeled n-set such that every point of the set is covered by exactly 3 subsets of the cover and that intersection of every 3 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 3.
%D For labeled case see Goulden I. P., Jackson D. M., Combinatorial Enumeration, John Wiley and Sons, New York, 1983.
%H Vladeta Jovovic, <a href="/A058790/a058790.pdf">Formula</a>
%Y Cf. A050535, A050913, A058783-A058785, A082789, A082790.
%A _Vladeta Jovovic_, Nov 30 2000
%E More terms from T. Forbes (anthony.d.forbes(AT)googlemail.com), May 24, 2003