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 A004199 #30 Mar 19 2025 07:42:03
%S A004199 1,0,2,0,1,3,0,0,1,4,0,0,1,2,5,0,0,0,1,2,6,0,0,0,1,1,3,7,0,0,0,0,1,2,
%T A004199 3,8,0,0,0,0,1,1,2,4,9,0,0,0,0,0,1,1,2,4,10,0,0,0,0,0,1,1,2,3,5,11,0,
%U A004199 0,0,0,0,0,1,1,2,3,5,12,0,0,0,0,0,0,1,1,1,2,3,6,13,0,0,0,0,0,0,0,1,1,2,2,4,6,14
%N A004199 Table of [ x/y ], where (x,y) = (1,1),(1,2),(2,1),(1,3),(2,2),(3,1),...
%C A004199 Entry in row n and column k is also the number of multiples of k less than or equal to n, n,k >= 1. - _L. Edson Jeffery_, Aug 31 2014
%F A004199 Sum_{k=1..n} a(n-k+1,k) = A002541(n+1).
%e A004199 Array begins:
%e A004199 1, 0, 0, 0, 0, 0, 0, 0, ...
%e A004199 2, 1, 0, 0, 0, 0, 0, 0, ...
%e A004199 3, 1, 1, 0, 0, 0, 0, 0, ...
%e A004199 4, 2, 1, 1, 0, 0, 0, 0, ...
%e A004199 5, 2, 1, 1, 1, 0, 0, 0, ...
%e A004199 ...
%t A004199 (* Array version: *)
%t A004199 Grid[Table[Floor[n/k], {n, 14}, {k, 14}]] (* _L. Edson Jeffery_, Aug 31 2014 *)
%t A004199 (* Array antidiagonals flattened: *)
%t A004199 Flatten[Table[Floor[(n - k + 1)/k], {n, 14}, {k, n}]] (* _L. Edson Jeffery_, Aug 31 2014 *)
%Y A004199 Cf. A002541 (antidiagonal sums).
%Y A004199 Cf. A010766 (same sequence as triangle, omitting the zeros), A010783.
%K A004199 tabl,nonn
%O A004199 1,3
%A A004199 _David W. Wilson_