OFFSET
0,2
LINKS
FORMULA
a(n) = Sum_{i=0..n} Sum_{j=0..n} C(n, i)^2*C(n, j)^2*C(n+i, n)*C(i+j, i).
PROG
(PARI) a(n)=sum(i=0, n, sum(j=0, n, binomial(n, i)^2*binomial(n, j)^2*binomial(n+i, n)*binomial(i+j, i)))
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Ralf Stephan, Sep 03 2004
STATUS
approved