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 A144220 #5 Jan 13 2022 01:37:04 %S A144220 1,2,-1,-3,1,1,-4,0,4,-1,5,2,-10,3,1,6,5,-20,5,6,-1,-7,-9,35,5,-21,5, %T A144220 1,-8,-14,56,0,-56,14,8,-1,9,20,-84,-14,126,-28,-36,7,1,10,27,-120, %U A144220 -42,252,-42,-120,27,10,-1,-11,-35,165,90,-462,42,330,-75,-55,9,1 %N A144220 Triangle read by rows, A118433 (the self-inverse triangle) * A000012^(-1). %C A144220 Row sums = (1, 1, -1, -1, 1, 1, ...). %F A144220 A118433 * A000012^(-1), where A000012^(-1) is an infinite lower triangular matrix with 1's in the main diagonal and (-1)'s in the subdiagonal, with the rest zeros. %e A144220 First few rows of the triangle: %e A144220 1; %e A144220 2, -1; %e A144220 3, 1, 1; %e A144220 -4, 0, 4, -1 %e A144220 5, 2, -10, 3, 1; %e A144220 6, 5, -20, 5, 6, -1; %e A144220 -7, -9, 35, -5, -21, 5, 1; %e A144220 -8, -14, 56, 0, -56, 14, 8, -1; %e A144220 9, 20, -84, -14, 126, -28, -36, 7, 1; %e A144220 10, 27, -120, -42, 252, -42, -120, 27, 10, -1; %e A144220 ... %Y A144220 Cf. A118433. %K A144220 tabl,sign %O A144220 0,2 %A A144220 _Gary W. Adamson_, Sep 14 2008