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 A057964 #6 Feb 16 2025 08:32:43 %S A057964 1,16,6,160,120,25,1280,1440,600,90,8960,13440,8400,2520,301,57344, %T A057964 107520,89600,40320,9632,966,344064,774144,806400,483840,173376,34776, %U A057964 3025,1966080,5160960,6451200,4838400,2311680,695520,121000,9330 %N A057964 Triangle T(n,k) of number of minimal 3-covers of a labeled n-set that cover k points of that set uniquely (k=3,..,n). %C A057964 Row sums give A003468. %H A057964 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/MinimalCover.html">Minimal cover</a> %F A057964 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 A057964 [1], [16, 6], [160, 120, 25], [1280, 1440, 600, 90], ...; There are 305=160+120+25 minimal 3-covers of a labeled 5-set. %Y A057964 Cf. A035347, A057669 (unlabeled case), A057963, A057965-A057968. %K A057964 easy,nonn,tabl %O A057964 3,2 %A A057964 _Vladeta Jovovic_, Oct 17 2000