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 A333158 #5 Mar 09 2020 21:18:38 %S A333158 1,0,1,1,1,1,1,1,0,2,0,1,1,3,8,8,3,1,1,0,38,0,38,0,1,1,15,208,730,730, %T A333158 208,15,1,1,0,1348,0,20670,0,1348,0,1,1,105,10126,188790,781578, %U A333158 781578,188790,10126,105,1,1,0,86174,0,37885204,0,37885204,0,86174,0,1 %N A333158 Irregular triangle read by rows: T(n,k) is the number of k-regular graphs on n labeled nodes with loops allowed, n >= 1, 0 <= k <= n + 1. %C A333158 A loop adds 2 to the degree of its vertex. %F A333158 T(n,k) = T(n, n+1-k). %e A333158 Triangle begins: %e A333158 1, 0, 1; %e A333158 1, 1, 1, 1; %e A333158 1, 0, 2, 0, 1; %e A333158 1, 3, 8, 8, 3, 1; %e A333158 1, 0, 38, 0, 38, 0, 1; %e A333158 1, 15, 208, 730, 730, 208, 15, 1; %e A333158 1, 0, 1348, 0, 20670, 0, 1348, 0, 1; %e A333158 1, 105, 10126, 188790, 781578, 781578, 188790, 10126, 105, 1; %e A333158 ... %Y A333158 Row sums are A322635. %Y A333158 Columns k=0..4 are A000012, A123023, A108246, A110039 (with interspersed zeros), A228697. %Y A333158 Cf. A059441, A333157. %K A333158 nonn,tabf %O A333158 1,10 %A A333158 _Andrew Howroyd_, Mar 09 2020