A107113 Diagonal sums of A107111, viewed as a number triangle.

1, 1, 2, 3, 6, 11, 24, 52, 125, 307, 809, 2190, 6249, 18348, 56016, 176272, 571113, 1906091, 6517283, 22879944, 82144248, 301617448, 1131401427, 4327790902, 16886037207, 67073179408, 271242546501, 1115489848809, 4662462489619

Offset: 0

Author

Paul Barry, May 12 2005

Keywords

• easy
• nonn

Formula

a(n)=sum{k=0..floor(n/2), sum{j=0..k, binomial((n-2k)(k+1), k-j)*binomial(k+j, j)}/(k+1)}