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 A128489 #12 May 29 2023 13:00:15 %S A128489 1,3,1,6,1,1,10,3,1,1,15,3,1,1,1,21,6,3,1,1,1,28,6,3,1,1,1,1,36,10,3, %T A128489 3,1,1,1,1,45,10,6,3,1,1,1,1,1,55,15,6,3,3,1,1,1,1,1,66,15,6,3,3,1,1, %U A128489 1,1,1,1,78,21,10,6,3,3,1,1,1,1,1,1,91,21,10,6,3,3,1,1,1,1,1,1,1 %N A128489 Triangle read by rows: A000012 * A126988 as infinite lower triangular matrices. %C A128489 Row sums = A024916: (1, 4, 8, 15, 21, 33, ...). %F A128489 By columns, k=1,2,3,...; k repeated terms of the triangular series, (1, 3, 6, 10, ...) in the k-th column. %e A128489 First few rows of the triangle: %e A128489 1; %e A128489 3, 1; %e A128489 6, 1, 1; %e A128489 10, 3, 1, 1; %e A128489 15, 3, 1, 1, 1; %e A128489 21, 6, 3, 1, 1, 1; %e A128489 28, 6, 3, 1, 1, 1, 1; %e A128489 36, 10, 3, 3, 1, 1, 1, 1; %e A128489 45, 10, 6, 3, 1, 1, 1, 1, 1; %e A128489 ... %Y A128489 Cf. A000012, A000217, A024916, A126988. %K A128489 nonn,tabl %O A128489 1,2 %A A128489 _Gary W. Adamson_, Mar 04 2007 %E A128489 a(11) = 1 inserted and more terms from _Georg Fischer_, May 29 2023