This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A058790 #13 Jul 01 2025 19:26:03 %S A058790 1,3,12,66,445,4279,53340,846254,16333946,371976963,9763321109, %T A058790 290473143807,9674133467729,357177322891321,14503958827502886, %U A058790 643502334799711633,31018731336031551119,1616523352051185316626,90689288905913623412837,5456178840303106057314759,350830170593891706361540379 %N A058790 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 A058790 Cover may include multiple occurrences of a subset. Also n-rowed binary matrices with distinct rows and all row sums 3. %D A058790 For labeled case see Goulden I. P., Jackson D. M., Combinatorial Enumeration, John Wiley and Sons, New York, 1983. %H A058790 Vladeta Jovovic, <a href="/A058790/a058790.pdf">Formula</a> %Y A058790 Row n=3 of A331508. %Y A058790 Cf. A050535, A050913, A058783, A058784, A058785, A082789, A082790. %K A058790 nonn %O A058790 1,2 %A A058790 _Vladeta Jovovic_, Nov 30 2000 %E A058790 More terms from T. Forbes (anthony.d.forbes(AT)googlemail.com), May 24 2003