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 A131875 #8 Mar 04 2022 11:18:29 %S A131875 1,5,4,12,5,7,22,6,8,10,35,7,9,11,13,51,8,10,12,14,16,70,9,11,13,15, %T A131875 17,19,92,10,12,14,16,18,20,22,117,11,13,15,17,19,21,23,25,145,12,14, %U A131875 16,18,20,22,24,26,28 %N A131875 Triangle, A000012 * A131844 as infinite lower triangular matrices. %C A131875 Left column = pentagonal numbers, A000326: (1, 5, 12, 22, ...). %C A131875 Row sums = A001106: (1, 9, 24, 46, 75, 111, ...). %e A131875 First few rows of the triangle: %e A131875 1; %e A131875 5, 4; %e A131875 12, 5, 7; %e A131875 22, 6, 8, 10; %e A131875 35, 7, 9, 11, 13; %e A131875 51, 8, 10, 12, 14, 16; %e A131875 70, 9, 11, 13, 15, 17, 19; %e A131875 92, 10, 12, 14, 16, 18, 20, 22; %e A131875 ... %Y A131875 Cf. A131844, A001106, A000326. %K A131875 nonn,tabl %O A131875 0,2 %A A131875 _Gary W. Adamson_, Jul 22 2007