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 A131899 #6 Mar 04 2022 02:06:05 %S A131899 1,2,3,3,2,5,4,2,3,7,5,2,3,4,9,6,2,3,4,5,11,7,2,3,4,5,6,13,8,2,3,4,5, %T A131899 6,7,15,9,2,3,4,5,6,7,8,17,10,2,3,4,5,6,7,8,9,19 %N A131899 A002260 + A131821 - A000012. %C A131899 Row sums = A052905: (1, 5, 10, 16, 23, ...) %F A131899 A002260 + A131821 - A000012 as infinite lower triangular matrices. %e A131899 First few rows of the triangle: %e A131899 1; %e A131899 2, 3; %e A131899 3, 2, 5; %e A131899 4, 2, 3, 7; %e A131899 5, 2, 3, 4, 9; %e A131899 6, 2, 3, 4, 5, 11; %e A131899 7, 2, 3, 4, 5, 6, 13; %e A131899 ... %Y A131899 Cf. A002260, A131821, A052905. %K A131899 nonn,tabl %O A131899 0,2 %A A131899 _Gary W. Adamson_, Jul 25 2007