OFFSET
0,2
PROG
(PARI) {a(n)=local(M=matrix(n+1, n+1, r, c, if(r>=c, binomial((r-1)*r*(r+1)/3!-(c-1)*c*(c+1)/3!, r-c))), N=matrix(n+1, n+1, r, c, if(r>=c, binomial((r-1)*r*(r+1)/3!-(c-1)*c*(c+1)/3!+1, r-c)))); sum(k=0, n, (N*M^-1)[n+1, k+1])}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Dec 27 2006
STATUS
approved