OFFSET
1,3
FORMULA
E.g.f.: Sum_{k>=1} Sum_{j>=1} mu(j) * x^(k*j) / (j!)^k).
E.g.f.: Sum_{k>=1} mu(k) * x^k / (k! - x^k).
a(n) ~ n!. - Vaclav Kotesovec, Feb 16 2020
MATHEMATICA
Table[n! DivisorSum[n, MoebiusMu[#]/(#!)^(n/#) &], {n, 1, 22}]
nmax = 22; CoefficientList[Series[Sum[MoebiusMu[k] x^k/(k! - x^k), {k, 1, nmax}], {x, 0, nmax}], x] Range[0, nmax]! // Rest
PROG
(PARI) a(n)={sumdiv(n, d, moebius(d)*n!/(d!)^(n/d))} \\ Andrew Howroyd, Feb 13 2020
(Magma) [Factorial(n)*&+[MoebiusMu(d) /(Factorial(d))^(n div d):d in Divisors(n)]:n in [1..22]]; // Marius A. Burtea, Feb 13 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Feb 13 2020
STATUS
approved