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 A131304 #4 Mar 03 2022 23:49:24 %S A131304 1,3,1,5,5,1,7,3,3,1,9,13,5,3,1,11,15,7,5,3,1,13,11,11,9,5,3,1,15,7,9, %T A131304 7,9,5,3,1,17,9,13,11,11,11,5,3,1,19,33,15,137,9,11,5,3,1 %N A131304 2*A089840 - A000012. %F A131304 2*A089840(deleting the right border of zeros) - A000012. %e A131304 First few rows of the triangle: %e A131304 1; %e A131304 3, 1; %e A131304 5, 5, 1; %e A131304 7, 3, 3, 1; %e A131304 9, 13, 5, 3, 1; %e A131304 11, 15, 7, 5, 3, 1; %e A131304 13, 11, 11, 9, 5, 3, 1; %e A131304 ... %Y A131304 Cf. A089840, A131302, A131303, A122203, A122204. %K A131304 nonn,tabl %O A131304 1,2 %A A131304 _Gary W. Adamson_, Jun 27 2007