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 A128409 #11 Jun 08 2023 08:49:57 %S A128409 1,0,-1,-1,-1,-1,-1,-1,-1,0,-2,-1,-1,0,-1,-1,0,0,0,-1,1,-2,0,0,0,-1,1, %T A128409 -1,-2,0,0,0,-1,1,-1,0,-2,0,0,0,-1,1,-1,0,0,-1,1,0,0,0,1,-1,0,0,1,-2, %U A128409 1,0,0,0,1,-1,0,0,1,-1,-2,1,0,0,0,1,-1,0,0,1,-1,0,-3,1,0,0,0,1,-1,0,0,1,-1,0,-1 %N A128409 Triangle read by rows: A000012 * A128408 as infinite lower triangular matrices. %C A128409 Left border = the Mertens sequence: A002321: (1, 0, -1, -1, -2, ...). %C A128409 Right border = mu(n), A008683: (1, -1, -1, 0, -1, 1, -1, ...). %C A128409 Row sums = A062563: (1, -1, -3, -3, -5, -1, -3, ...). %e A128409 First few rows of the triangle: %e A128409 1; %e A128409 0, -1; %e A128409 -1, -1, -1; %e A128409 -1, -1, -1, 0; %e A128409 -2, -1, -1, 0, -1; %e A128409 -1, 0, 0, 0, -1, 1; %e A128409 -2, 0, 0, 0, -1, 1, -1; %e A128409 ... %Y A128409 Cf. A002321, A008683, A062563, A128407, A128408. %K A128409 tabl,sign %O A128409 1,11 %A A128409 _Gary W. Adamson_, Mar 01 2007 %E A128409 Previous a(51) = 0 removed and more terms from _Georg Fischer_, Jun 08 2023