OFFSET
0,2
FORMULA
a(n) = exp(1/(2*n)) * 2^n * n^n * Gamma(n+1, 1/(2*n)).
a(n) ~ 2^n * n^n * n!.
MATHEMATICA
Flatten[{1, Table[Sum[Binomial[n, k]*2^k*n^k*k!, {k, 0, n}], {n, 1, 20}]}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Vaclav Kotesovec, Oct 16 2016
STATUS
approved