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A137648
a(n) = Sum_{k=0..n} C(k^2, k) * C(k^2, n-k).
0
1, 1, 7, 108, 2612, 85298, 3501504, 172989880, 9987924928, 659768790882, 49065577842538, 4056413252138692, 369030922581806616, 36634832808175143734, 3940779041158898056286, 456592594401713997379344
OFFSET
0,3
MATHEMATICA
Table[Sum[Binomial[k^2, k]Binomial[k^2, n-k], {k, 0, n}], {n, 0, 20}] (* Harvey P. Dale, Dec 05 2012 *)
PROG
(PARI) a(n)=sum(k=0, n, binomial(k^2, k)*binomial(k^2, n-k))
CROSSREFS
Sequence in context: A218819 A033516 A130629 * A106977 A142480 A202515
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Jan 31 2008
STATUS
approved