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 A333739 #4 Apr 09 2020 12:30:38 %S A333739 1,1,3,23,641,62781,22393101,29445929253,144413237202513, %T A333739 2664174112921403401,186127457781265060985293, %U A333739 49509854244685925218197355989,50364892612276937755557718571828543,196663809308382999799947201118326883990475 %N A333739 Number of n X n nonnegative integer symmetric matrices with all row and column sums equal to n. %Y A333739 Main diagonal of A188403. %K A333739 nonn %O A333739 0,3 %A A333739 _Andrew Howroyd_, Apr 08 2020