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 A128137 #5 Feb 15 2022 01:54:39 %S A128137 1,-1,4,-1,1,9,-1,1,5,16,-1,1,5,11,25,-1,1,5,11,19,36,-1,1,5,11,19,29, %T A128137 49,-1,1,5,11,19,29,41,64,-1,1,5,11,19,29,41,55,81,-1,1,5,11,19,29,41, %U A128137 55,71,100 %N A128137 A002260 * A128132. %C A128137 Deleting the right and left borders gives terms of A028387: (1, 5, 11, 29, 29, 41, 55, 71, ...). Row sums = A064999: (1, 3, 9, 21, 41, ...). %F A128137 A002260 * A128132 as infinite lower triangular matrices. %e A128137 First few rows of the triangle: %e A128137 1; %e A128137 -1, 4; %e A128137 -1, 1, 9; %e A128137 -1, 1, 5, 16; %e A128137 -1, 1, 5, 11, 25; %e A128137 -1, 1, 5, 11, 19, 36; %e A128137 -1, 1, 5, 11, 19, 29, 49; %e A128137 ... %Y A128137 Cf. A002260, A128132, A028387, A128136, A064999. %K A128137 tabl,sign %O A128137 1,3 %A A128137 _Gary W. Adamson_, Feb 16 2007