OFFSET
0,2
FORMULA
a(n) = Sum_{k=0..n} C(k^2, k) * C((n-k)^2, n-k).
PROG
(PARI) a(n)=sum(k=0, n, binomial(k^2, k)*binomial((n-k)^2, n-k))
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Jan 29 2008
STATUS
approved