A246615 Number of endofunctions on [n] whose cycle lengths are multiples of 8.

1, 0, 0, 0, 0, 0, 0, 0, 5040, 362880, 18144000, 804988800, 34488115200, 1482082842240, 65120246231040, 2955402450000000, 139297568464454400, 6837892496270035200, 350034595015623598080, 18692451288585606954240, 1041114148173066240000000

Offset: 0

Author

Alois P. Heinz, Aug 31 2014

Keywords

• nonn

Links

• Alois P. Heinz, Table of n, a(n) for n = 0..300

Crossrefs

Column k=8 of A246609.

Programs

Maple

with(combinat):
b:= proc(n, i) option remember; `if`(n=0, 1,
      `if`(i>n, 0, add(b(n-i*j, i+8)*(i-1)!^j*
      multinomial(n, n-i*j, i$j)/j!, j=0..n/i)))
    end:
a:= a->add(b(j, 8)*n^(n-j)*binomial(n-1, j-1), j=0..n):
seq(a(n), n=0..25);

Mathematica

CoefficientList[Series[1/(1-LambertW[-x]^8)^(1/8),{x,0,20}],x] * Range[0,20]!  (* Vaclav Kotesovec, Sep 01 2014 *)

Formula

E.g.f.: 1/(1-LambertW(-x)^8)^(1/8). - Vaclav Kotesovec, Sep 01 2014

a(n) ~ n^(n-7/16) * 2^(1/16) * (sqrt(Pi) / Gamma(1/16)) * (1 - 161 * sqrt(2/n) * Gamma(1/16) / (768 * Gamma(9/16))). - Vaclav Kotesovec, Sep 01 2014