OFFSET
0,2
COMMENTS
PROG
(PARI) {a(n)=if(n==0, 2, polcoeff(2-sum(k=0, n-1, a(k)*x^k*prod(j=2, k\2+2, 1-j*x +x*O(x^n))), n))} /* at even-indices n=0, 2, 4, .. */
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Jan 21 2005
STATUS
approved