OFFSET
1,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..425
FORMULA
E.g.f.: Sum_{k>=1} x^k / (k! * (1 - k * x^k)).
MATHEMATICA
a[n_] := n! Sum[d^(n/d - 1)/d!, {d, Divisors[n]}]; Table[a[n], {n, 1, 22}]
nmax = 22; CoefficientList[Series[Sum[x^k/(k! (1 - k x^k)), {k, 1, nmax}], {x, 0, nmax}], x] Range[0, nmax]! // Rest
PROG
(PARI) a(n) = n! * sumdiv(n, d, d^(n/d - 1) / d!); \\ Michel Marcus, Sep 17 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Sep 17 2019
STATUS
approved