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 A131258 #4 Feb 18 2022 22:34:14 %S A131258 1,1,1,0,2,1,0,2,2,1,1,2,3,2,1,1,3,5,3,2,1,0,4,8,6,3,2,1,0,4,11,12,6, %T A131258 3,2,1,1,4,14,20,13,6,3,2,1,1,5,18,30,25,13,6,3,2,1 %N A131258 A129686^(-1) * A052509. %C A131258 Row sums = A097083: (1, 2, 3, 5, 9, 15, ...). %F A131258 A129686^(-1) * A052509 as infinite lower triangular matrices, where A129686 = the alternate term operator. %e A131258 First few rows of the triangle: %e A131258 1; %e A131258 1, 1; %e A131258 0, 2, 1; %e A131258 0, 2, 2, 1; %e A131258 1, 2, 3, 2, 1; %e A131258 1, 3, 5, 3, 2, 1; %e A131258 0, 4, 8, 6, 3, 2, 1; %e A131258 ... %Y A131258 Cf. A129686, A052509, A097083. %K A131258 nonn,tabl %O A131258 0,5 %A A131258 _Gary W. Adamson_, Jun 23 2007