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 A131901 #5 Mar 05 2022 01:08:11 %S A131901 1,2,2,3,5,3,4,7,7,4,5,9,9,9,5,6,11,11,11,11,6,7,13,13,13,13,13,7,8, %T A131901 15,15,15,15,15,15,8,9,17,17,17,17,17,17,17,9,10,19,19,19,19,19,19,19, %U A131901 19,10 %N A131901 2*A002024 - A131821. %C A131901 Row sums = A084849: (1, 4, 11, 22, 37, ...). %F A131901 2*A002024 - A131821 as infinite lower triangular matrices. %e A131901 First few rows of the triangle: %e A131901 1; %e A131901 2, 2; %e A131901 3, 5, 3; %e A131901 4, 7, 7, 4; %e A131901 5, 9, 9, 9, 5; %e A131901 6, 11, 11, 11, 11, 6; %e A131901 7, 13, 13, 13, 13, 13, 7; %e A131901 ... %Y A131901 Cf. A002024, A131821, A084849. %K A131901 nonn,tabl %O A131901 1,2 %A A131901 _Gary W. Adamson_, Jul 26 2007