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 A057965 #6 Feb 16 2025 08:32:43 %S A057965 1,55,10,1815,660,65,46585,25410,5005,350,1024870,745360,220220,30800, %T A057965 1701,20292426,18447660,7267260,1524600,168399,7770,372027810, %U A057965 405848520,199849650,55902000,9261945,854700,34105,6430766430 %N A057965 Triangle T(n,k) of number of minimal 4-covers of a labeled n-set that cover k points of that set uniquely (k=4,..,n). %C A057965 Row sums give A016111. %H A057965 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/MinimalCover.html">Minimal cover</a> %F A057965 Number of minimal m-covers of a labeled n-set that cover k points of that set uniquely is C(n, k)*S(k, m)*(2^m-m-1)^(n-k), where S(k, m) are Stirling numbers of the second kind. %e A057965 [1], [55, 10], [1815, 660, 65], [46585, 25410, 5005, 350], ...; there are 1815 minimal 4-covers of a labeled 6-set that cover 4 points of that set uniquely. %Y A057965 Cf. A035347, A057669, A057963, A057964, A057966, A057967(unlabeled case), A057968. %K A057965 easy,nonn,tabl %O A057965 4,2 %A A057965 _Vladeta Jovovic_, Oct 17 2000