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 A128220 #5 Feb 20 2022 15:16:54 %S A128220 1,3,2,4,4,3,5,5,5,4,6,6,6,6,5,7,7,7,7,7,6,8,8,8,8,8,8,7,9,9,9,9,9,9, %T A128220 9,8,10,10,10,10,10,10,10,10,9,11,11,11,11,11,11,11,11,11,10 %N A128220 Triangle, A127701 * A000012. %C A128220 Row sums = A028387: (1, 5, 11, 19, 29, 41, 55, ...) A000012 * A127701 = A128219. %F A128220 A127701 * A000012 as infinite lower triangular matrices. Triangle read by rows: a(1) = 1; n-th row = (n-1) terms of (n+1) followed by "n". %e A128220 First few rows of the triangle: %e A128220 1; %e A128220 3, 2; %e A128220 4, 4, 3; %e A128220 5, 5, 5, 4; %e A128220 6, 6, 6, 6, 5; %e A128220 7, 7, 7, 7, 7, 6; %e A128220 ... %Y A128220 Cf. A128219, A000012, A127701, A028387. %K A128220 nonn,tabl %O A128220 1,2 %A A128220 _Gary W. Adamson_, Feb 19 2007