%I #3 Mar 30 2012 18:59:07
%S 1,1,2,3,6,11,24,52,125,307,809,2190,6249,18348,56016,176272,571113,
%T 1906091,6517283,22879944,82144248,301617448,1131401427,4327790902,
%U 16886037207,67073179408,271242546501,1115489848809,4662462489619
%N Diagonal sums of A107111, viewed as a number triangle.
%F 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)}
%K easy,nonn
%O 0,3
%A _Paul Barry_, May 12 2005