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 A107027 #12 Mar 16 2025 12:42:24
%S A107027 1,1,2,1,2,2,1,2,4,2,1,2,6,8,2,1,2,8,20,16,2,1,2,10,38,70,32,2,1,2,12,
%T A107027 62,196,252,64,2,1,2,14,92,426,1062,924,128,2,1,2,16,128,792,3112,
%U A107027 5948,3432,256,2,1,2,18,170,1326,7302,23686,34120,12870,512,2
%N A107027 Number triangle associated to the Riordan arrays (1/(1+x),x/(1+x)^k),k>=0.
%C A107027 As a number square read by antidiagonals, the rows represent the row sums of the inverses of the Riordan arrays (1/(1+x),x/(1+x)^k), k>=0. The rows are then given by T(n,k)=(n-1)C(n*k,k)-(n-2)*sum{j=0..k, C(n*k,j)}.
%F A107027 Number triangle T(n, k)=if(k<=n, (n-k-1)C((n-k)*k, k)-(n-k-2)*sum{j=0..k, C((n-k)*k, j)}, 0).
%e A107027 Triangle begins
%e A107027 1;
%e A107027 1, 2;
%e A107027 1, 2, 2;
%e A107027 1, 2, 4, 2;
%e A107027 1, 2, 6, 8, 2;
%e A107027 1, 2, 8, 20, 16, 2;
%Y A107027 T(n,n) is A040000, T(n+1,n) is A000079, T(n+2,n) is A000984, T(n+3,n) is A047098.
%Y A107027 The reverse of this triangle is A107030.
%Y A107027 Row sums are A107028.
%Y A107027 Diagonal sums are A107029.
%K A107027 easy,nonn,tabl
%O A107027 0,3
%A A107027 _Paul Barry_, May 09 2005