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 A131399 #2 Mar 30 2012 17:25:22 %S A131399 1,1,1,1,4,1,1,6,6,1,1,9,12,9,1,1,11,23,23,11,1,1,14,34,52,34,14,1,1, %T A131399 16,51,90,90,51,16,1,1,19,67,152,180,152,67,19,1,1,21,90,225,342,342, %U A131399 225,90,21,1 %N A131399 3*A007318 - A046854 - A065941. %C A131399 Row sums = A074878: (1, 2, 6, 14, 32, 70, 150,...). %F A131399 3*A007318 - A046854 - A065941 as infinite lower triangular matrices. %e A131399 First few rows of the triangle are: %e A131399 1; %e A131399 1, 1; %e A131399 1, 4, 1; %e A131399 1, 6, 6, 1; %e A131399 1, 9, 12, 9, 1; %e A131399 1, 11, 23, 23, 11, 1; %e A131399 1, 14, 34, 52, 34, 14, 1; %e A131399 1, 16, 51, 90, 90, 51, 16, 1; %e A131399 ... %Y A131399 Cf. A007318, A046854, A065941, A074878. %K A131399 nonn,tabl %O A131399 0,5 %A A131399 _Gary W. Adamson_, Jul 05 2007