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 A350912 #16 Apr 04 2022 10:17:16 %S A350912 1,1,1,1,0,2,1,1,4,4,1,0,4,0,12,1,1,12,62,112,56,1,0,18,0,1602,0,456, %T A350912 1,1,40,2062,32263,92980,46791,6880,1,0,68,0,748576,0,11210264,0, %U A350912 191536,1,1,140,103827,19349672,616991524,3319462470,2729098064,292115960,9733056 %N A350912 Triangle read by rows: T(n,k) is the number of oriented graphs on n unlabeled nodes whose underlying graph is k-regular, k = 0..n-1. %C A350912 The sum of the in-degree and out-degree at each node is k. %C A350912 a(2*n,2*n-2) is the number of orientations (up to isomorphism) of the n-cocktail party graph. - _Pontus von Brömssen_, Apr 03 2022 %H A350912 Andrew Howroyd, <a href="/A350912/b350912.txt">Table of n, a(n) for n = 1..253</a> (rows 1..22) %e A350912 Triangle begins: %e A350912 1; %e A350912 1, 1; %e A350912 1, 0, 2; %e A350912 1, 1, 4, 4; %e A350912 1, 0, 4, 0, 12; %e A350912 1, 1, 12, 62, 112, 56; %e A350912 1, 0, 18, 0, 1602, 0, 456; %e A350912 ... %Y A350912 Row sums are A350913. %Y A350912 Main diagonal is A000568. %Y A350912 The labeled version is A351263. %Y A350912 Cf. A051031 (graphs), A350910 (digraphs). %K A350912 nonn,tabl %O A350912 1,6 %A A350912 _Andrew Howroyd_, Jan 29 2022