A132960 a(n) = n!*Sum_{d|n} (-1)^(d+1)/(d!*(n/d)^d).

1, 0, 3, 2, 25, 94, 721, 3674, 42561, 291248, 3628801, 34254604, 479001601, 5337581534, 88966701825, 1140807642974, 20922789888001, 321094542593824, 6402373705728001, 109338195253235948, 2457732174030848001

Offset: 1

Author

Vladeta Jovovic, Sep 06 2007

Keywords

• easy
• nonn

Links

• G. C. Greubel, Table of n, a(n) for n = 1..450

Crossrefs

Cf. A005225, A132958, A132959, A132961, A132962, A132963.

Programs

Mathematica

Rest[ Range[0, 22]! CoefficientList[ Series[ - Sum[ Exp[ -x^k/k], {k, 25}], {x, 0, 22}], x]] (* Robert G. Wilson v, Sep 13 2007 *)

PARI

a(n) = n!*sumdiv(n, d, (-1)^(d+1)/(d!*(n/d)^d)); \\ Michel Marcus, Sep 29 2017

Formula

E.g.f.: Sum_{k>0}(1-exp(-x^k/k)).

Extensions

More terms from Robert G. Wilson v, Sep 13 2007