OFFSET
0,3
FORMULA
a(n) ~ 2^(n-5/2) * exp(n-5/4) * n^(n-7/2) / sqrt(Pi). - Vaclav Kotesovec, Mar 06 2014
MATHEMATICA
Flatten[{1, Table[Sum[Binomial[n^2+k^2, k]*(n-k)^2/(n^2+k^2), {k, 0, n-1}], {n, 1, 20}]}] (* Vaclav Kotesovec, Mar 06 2014 *)
PROG
(PARI) {a(n)=if(n<0, 0, 0^n+sum(k=0, n-1, binomial(n^2+k^2, k)*(n-k)^2/(n^2+k^2)))}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Jan 15 2011
STATUS
approved