OFFSET
0,2
COMMENTS
FORMULA
EXAMPLE
PROG
(PARI) {a(n)=sum(k=0, n, binomial(n, k)* if(k\2==0, 1, sum(j=0, k\2-1, binomial(k\2-1, j)^2* sum(i=0, 2*j, (-1)^(2*j-i)*binomial(2*j, i)*a(i)))))}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Dec 06 2004
STATUS
approved