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 A131843 #8 Dec 25 2016 02:18:14 %S A131843 1,3,3,5,1,5,7,1,1,7,9,1,1,1,9,11,1,1,1,1,11,13,1,1,1,1,1,13,15,1,1,1, %T A131843 1,1,1,15,17,1,1,1,1,1,1,1,17,19,1,1,1,1,1,1,1,1,19,21,1,1,1,1,1,1,1, %U A131843 1,1,21,23,1,1,1,1,1,1,1,1,1,1,23,25,1,1,1,1,1,1,1,1,1,1,1,25,27,1,1,1,1,1 %N A131843 Triangle read by rows: 2*A131821 - A000012. %C A131843 Row sums = 5*n + 1, A016861: (1, 6, 11, 16, 21, ...). %H A131843 B. D. Swan, <a href="/A131843/b131843.txt">Table of n, a(n) for n = 0..100000</a> %F A131843 2*A131821 - A000012 as an infinite lower triangular matrix. 2*n - 1, (1, 3, 5, 7, ...) as right and left borders, with the rest zeros. %e A131843 First few rows of the triangle are: %e A131843 1; %e A131843 3, 3; %e A131843 5, 1, 5; %e A131843 7, 1, 1, 7; %e A131843 9, 1, 1, 1, 9; %e A131843 11, 1, 1, 1, 1, 11; %e A131843 ... %Y A131843 Cf. A016861, A131821. %K A131843 nonn,tabl,easy %O A131843 0,2 %A A131843 _Gary W. Adamson_, Jul 21 2007 %E A131843 Corrected and edited by B. D. Swan (bdswan(AT)gmail.com), Dec 20 2008