OFFSET
0,2
COMMENTS
PROG
(PARI) {a(n)=local(F=x, M, N, P); M=matrix(n+5, n+5, r, c, F=x; for(i=1, r+c-2, F=subst(F, x, x+x^2+x*O(x^(n+5)))); polcoeff(F, c)); N=matrix(n+4, n+4, r, c, F=x; for(i=1, r, F=subst(F, x, x+x^2+x*O(x^(n+5)))); polcoeff(F, c)); P=matrix(n+4, n+4, r, c, M[r+1, c]); (P~*N~^-1)[n+4, 4]}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Nov 27 2009
STATUS
approved