OFFSET
1,3
LINKS
Winston de Greef, Table of n, a(n) for n = 1..448
FORMULA
E.g.f.: Sum_{k>=1} mu(k) * (exp(x^k) - 1).
Sum_{n>=1} a(n) * x^n / (n! * (1 - x^n)) = exp(x) - 1.
MATHEMATICA
Table[n! Sum[MoebiusMu[n/d]/d!, {d, Divisors[n]}], {n, 1, 22}]
nmax = 22; CoefficientList[Series[Sum[MoebiusMu[k] (Exp[x^k] - 1), {k, 1, nmax}], {x, 0, nmax}], x] Range[0, nmax]! // Rest
PROG
(PARI) a(n)=n! * sumdiv(n, d, moebius(n/d) / d!) \\ Winston de Greef, Sep 19 2023
CROSSREFS
KEYWORD
sign
AUTHOR
Ilya Gutkovskiy, May 14 2022
STATUS
approved