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 A135723 #6 Mar 27 2022 23:29:32 %S A135723 1,1,1,1,1,2,1,1,2,5,1,1,1,11,14,1,1,1,9,71,42,1,1,1,5,161,425,132,1, %T A135723 1,1,2,251,1979,2383,429,1,1,1,1,303,6277,19509,12805,1430,1,1,1,1, %U A135723 299,15675,106493,168609,66947,4862 %N A135723 A122890 + A000012 - I, I = Identity matrix. %C A135723 Row sums = A005095: (1, 2, 4, 9, 28, 125, 726, ...). %C A135723 Main diagonal = A000108, the Catalan numbers: (1, 1, 2, 5, 14, 42, 132, ...). %F A135723 A122890 + A000012 - Identity matrix; as infinite lower triangular matrices. %e A135723 First few rows of the triangle: %e A135723 1; %e A135723 1, 1; %e A135723 1, 1, 2; %e A135723 1, 1, 2, 5; %e A135723 1, 1, 1, 11, 14; %e A135723 1, 1, 1, 9, 71, 42; %e A135723 1, 1, 1, 5, 161, 425, 132; %e A135723 1, 1, 1, 2, 251, 1979, 2383, 429; %e A135723 ... %Y A135723 Cf. A122890, A005095, A000108. %K A135723 nonn,tabl %O A135723 0,6 %A A135723 _Gary W. Adamson_, Nov 25 2007