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 A134249 #8 Feb 08 2022 20:13:57 %S A134249 1,3,1,5,7,1,8,10,13,1,12,14,17,21,1,17,19,22,26,31,1,23,25,28,32,37, %T A134249 43,1,30,32,35,39,44,50,57,1,38,40,43,47,52,58,65,73,1,47,49,52,56,61, %U A134249 67,74,82,91,1 %N A134249 Triangle read by rows, taken from the lower triangular matrix (M * A000012 + A000012 * M) - A000012; where M = lower triangular matrix with (1,1,1,...) in the main diagonal and the triangular numbers in the subdiagonal and A000012 = (1; 1,1; 1,1,1; ...). %C A134249 Row sums = A037235: (1, 4, 13, 32, 65, 116, ...). Left column = A134250: (1, 3, 5, 8, 12, 17, 23, ...). %e A134249 First few rows of the triangle: %e A134249 1; %e A134249 3, 1; %e A134249 5, 7, 1; %e A134249 8, 10, 13, 1; %e A134249 12, 14, 17, 21, 1; %e A134249 17, 19, 22, 26, 31, 1; %e A134249 23, 25, 28, 32, 37, 43, 1; %e A134249 ... %Y A134249 Cf. A037235, A134250. %K A134249 nonn,tabl %O A134249 1,2 %A A134249 _Gary W. Adamson_, Oct 15 2007 %E A134249 Edited by _N. J. A. Sloane_, Nov 01 2009