OFFSET
0,3
COMMENTS
PROG
(PARI) {a(n)=if(n==0, 1, sum(k=0, n\2, 2^(n-2*k-1)*binomial(n-1, 2*k)*binomial(2*k, k)/(k+1)*a(k)))}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, May 06 2006
STATUS
approved