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 A128078 #5 Feb 15 2022 02:03:59 %S A128078 1,-1,4,-1,-2,9,-1,-2,-3,16,-1,-2,-3,-4,25,-1,-2,-3,-4,-5,36,-1,-2,-3, %T A128078 -4,-5,-6,49,-1,-2,-3,-4,-5,-6,-7,64 %N A128078 A002260 * A128064. %C A128078 Row sums = the triangular numbers: (1, 3, 6, 10, ...). %C A128078 Row sums of A128077 = A000326, the pentagonal numbers: (1, 5, 12, 22, 35, ...). %F A128078 A002260 * A128064 as infinite lower triangular matrices. Retain the right border of A128077 and change the signs of all other terms to (-). %e A128078 First few rows of the triangle: %e A128078 1; %e A128078 -1, 4; %e A128078 -1, -2, 9; %e A128078 -1, -2, -3, 16; %e A128078 ... %Y A128078 Cf. A002260, A128064, A128077, A000326. %K A128078 tabl,sign %O A128078 1,3 %A A128078 _Gary W. Adamson_, Feb 14 2007