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 A135858 #5 Mar 27 2022 22:25:40 %S A135858 1,3,1,7,5,1,13,13,7,1,21,21,21,9,1,31,31,31,31,11,1,43,43,43,43,43, %T A135858 13,1,57,57,57,57,57,57,15,1,73,73,73,73,73,73,73,17,1,91,91,91,91,91, %U A135858 91,91,91,19,1 %N A135858 A128229^2 * A000012. %C A135858 Row sums = A135859: (1, 4, 13, 34, 73, 136, ...). %F A135858 A128229^2 * A000012, where A128229 = a bidiagonal matrix with all 1's in the main diagonal and (1, 2, 3, ...) in the subdiagonal. %e A135858 First few rows of the triangle: %e A135858 1; %e A135858 3, 1; %e A135858 7, 5, 1; %e A135858 13, 13, 7, 1; %e A135858 21, 21, 21, 9, 1; %e A135858 31, 31, 31, 31, 11, 1; %e A135858 43, 43, 43, 43, 43, 13, 1; %e A135858 ... %Y A135858 Cf. A128229, A135859. %K A135858 nonn,tabl %O A135858 1,2 %A A135858 _Gary W. Adamson_, Dec 01 2007