OFFSET
0,2
FORMULA
PROG
(PARI) {a(n)=local(H=Mat(1), B); for(m=1, n+3, B=matrix(m, m); for(i=1, m, for(j=1, i, if(j==i, B[i, j]=1, B[i, j]=(H^i)[i-1, j]); )); H=B); return((H^(n+1))[n+3, 3])}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Aug 26 2006
STATUS
approved