A030799 a(n) = floor(exp(1/2)*n!).

1, 3, 9, 39, 197, 1187, 8309, 66476, 598287, 5982879, 65811677, 789740126, 10266621646, 143732703044, 2155990545670, 34495848730735, 586429428422497, 10555729711604956, 200558864520494172, 4011177290409883459

Offset: 1

Author

Simon Plouffe

Keywords

• nonn

Links

• Robert Israel, Table of n, a(n) for n = 1..449

Crossrefs

Cf. A068453.

Programs

Maple

f:= n -> floor(exp(1/2)*n!):
map(f, [$1..30]); # Robert Israel, Oct 16 2019

Mathematica

Floor[Exp[1/2]Range[20]!] (* Harvey P. Dale, Aug 19 2020 *)

Formula

a(n+1) = (n+1)*a(n) + A068453(n+1). - Robert Israel, Oct 16 2019