A261779 a(n) = ceiling((n-1)! / n).

1, 1, 1, 2, 5, 20, 103, 630, 4480, 36288, 329891, 3326400, 36846277, 444787200, 5811886080, 81729648000, 1230752346353, 19760412672000, 336967037143579, 6082255020441600, 115852476579840000, 2322315553259520000, 48869596859895986087, 1077167364120207360000, 24817936069329577574400, 596585001666576384000000

Offset: 1

Author

Franklin T. Adams-Watters, Aug 31 2015

Keywords

• nonn

Comments

Except for n = 4, this is ((n-1)!+1)/n for prime n, and (n-1)!/n otherwise.

Crossrefs

Cf. A007619 (prime index elements).

Programs

Mathematica

Table[Ceiling[((n-1)!)/n],{n,30}] (* Harvey P. Dale, Oct 04 2018 *)

PARI

a(n) = ceil((n-1)!/n)