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 A131257 #18 Jun 05 2023 09:04:17 %S A131257 1,0,1,0,1,1,-1,2,1,1,0,1,3,1,1,0,1,4,3,1,1,1,0,6,5,3,1,1,0,1,6,10,5, %T A131257 3,1,1,0,1,7,15,11,5,3,1,1,-1,2,7,22,20,11,5,3,1,1,0,1,9,28,36,21,11, %U A131257 5,3,1,1,0,1,10,36,57,42,21,11,5,3,1,1,1,0,12,44,86,77,43,21,11,5,3,1,1 %N A131257 Triangle read by rows: A052509 * A097807 as infinite lower triangular matrices. %C A131257 Row sums give A099517. %F A131257 A052509 * A000012 (signed, + - + - by columns). %e A131257 First few rows of the triangle: %e A131257 1; %e A131257 0, 1; %e A131257 0, 1, 1; %e A131257 -1, 2, 1, 1; %e A131257 0, 1, 3, 1, 1; %e A131257 0, 1, 4, 3, 1, 1; %e A131257 1, 0, 6, 5, 3, 1, 1; %e A131257 ... %Y A131257 Cf. A099517, A052509, A097807, A131256. %K A131257 tabl,sign %O A131257 0,8 %A A131257 _Gary W. Adamson_, Jun 23 2007 %E A131257 a(48) = 22 corrected and more terms from _Georg Fischer_, Jun 05 2023