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 A131241 #4 Feb 26 2022 00:36:34 %S A131241 1,3,1,3,3,1,3,6,3,1,3,6,9,3,1,3,9,9,12,3,1,3,9,18,12,15,3,1,3,12,18, %T A131241 30,15,18,3,1,3,12,30,30,45,18,21,3,1,3,15,30,60,45,63,21,24,3,1 %N A131241 3*A046854 - 2*I. %C A131241 Row sums = A111314: (1, 4, 7, 13, 22, 37, ...). A131240 = 2*A046854 - I. %F A131241 3*A046854 - 2*I, where A046854 = Pascal's triangle with repeats by columns and I = Identity matrix. %e A131241 First few rows of the triangle: %e A131241 1; %e A131241 3, 1; %e A131241 3, 3, 1; %e A131241 3, 6, 3, 1; %e A131241 3, 6, 9, 3, 1; %e A131241 3, 9, 9, 12, 3, 1 %e A131241 3, 9, 18, 12, 15, 3, 1; %e A131241 ... %Y A131241 Cf. A046854, A111314, A131240. %K A131241 nonn,tabl %O A131241 0,2 %A A131241 _Gary W. Adamson_, Jun 21 2007