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 A131781 #9 Mar 04 2022 11:18:56 %S A131781 1,3,1,1,3,1,3,3,3,1,1,5,5,3,1,3,5,7,7,3,1,1,7,11,9,9,3,1,3,7,13,19, %T A131781 11,11,3,1,1,9,19,21,29,13,13,3,1,3,9,21,39,31,41,15,15,3,1 %N A131781 2*A046854 - A000012 (signed by columns + - + -, ...). %C A131781 Row sums = A131780: (1, 4, 5, 10, 15, 26, 41, ...), a sequence with a(n)/a(n-1) tending to phi. %C A131781 A131779 is a companion triangle, same row sums. %e A131781 First few rows of the triangle: %e A131781 1; %e A131781 3, 1; %e A131781 1, 3, 1; %e A131781 3, 3, 3, 1; %e A131781 1, 5, 5, 3, 1; %e A131781 3, 5, 7, 7, 3, 1; %e A131781 1, 7, 11, 9, 9, 3, 1; %e A131781 3, 7, 13, 19, 11, 11, 3, 1; %e A131781 ... %Y A131781 Cf. A131779, A131780, A046854, A000012. %K A131781 nonn,tabl %O A131781 1,2 %A A131781 _Gary W. Adamson_, Jul 14 2007