OFFSET
0,2
LINKS
Harvey P. Dale, Table of n, a(n) for n = 0..333
FORMULA
a(n) ~ c * d^n * (n-1)!, where d = 4/(LambertW(2*exp(-2))*(2 + LambertW(2*exp(-2)))) and c = 0.26357096872357954619128367188797403780111321551104973353361235838... - Vaclav Kotesovec, Oct 05 2020
MATHEMATICA
Table[Sum[Binomial[k(k+1), k]Binomial[k(k+1), n-k], {k, 0, n}], {n, 0, 20}] (* Harvey P. Dale, Dec 11 2018 *)
PROG
(PARI) a(n)=sum(k=0, n, binomial(k*(k+1), k)*binomial(k*(k+1), n-k))
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Jan 31 2008
STATUS
approved