OFFSET
1,1
COMMENTS
PROG
(PARI) {a(n)=local(A=x, G=x*(1+x*y)/(1-x)); for(i=1, n+1, A=subst(G, x, A+O(x^(n+2)))); polcoeff(polcoeff(A, n+1, x), 1, y)}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Feb 03 2011
STATUS
approved