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 A331721 #5 Feb 01 2020 13:39:43 %S A331721 1,5,66,1338,43686,2142277,149056260,13991691663,1705750869937, %T A331721 262268740077763,49694977078927305,11388565848749818055, %U A331721 3107918736854019004136,996840601151518793573156,371595543159269706775806375,159437222426663041455988930042,78072200940916732097886063687252 %N A331721 Number of nonequivalent n-column nonnegative integer matrices with column sums 4 and any number of nonzero rows up to permutation of rows and columns. %Y A331721 Row n=4 of A331485. %K A331721 nonn %O A331721 0,2 %A A331721 _Andrew Howroyd_, Jan 31 2020