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 A136581 #4 Mar 27 2022 19:07:52 %S A136581 1,0,1,2,0,2,0,6,0,6,24,0,24,0,24,0,120,0,120,0,120,720,0,720,0,720,0, %T A136581 720,0,5040,0,5040,0,5040,0,5040 %N A136581 Triangle read by rows: A136572 * A128174. %C A136581 Row sums = A052558: (1, 1, 4, 12, 72, 360, ...). %F A136581 A136572 * A128174 as infinite lower triangular matrices. %e A136581 First few rows of the triangle: %e A136581 1; %e A136581 0, 1; %e A136581 2, 0, 2; %e A136581 0, 6, 0, 6; %e A136581 24, 0, 24, 0, 24; %e A136581 0, 120, 0, 120, 0, 120; %e A136581 ... %Y A136581 Cf. A000142, A052558, A128174, A136572. %K A136581 nonn,tabl %O A136581 0,4 %A A136581 _Gary W. Adamson_, Jan 09 2008