OFFSET
1,4
COMMENTS
A kind of Dirichlet convolution of mu(n) with Bell numbers.
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..100
MATHEMATICA
a[n_] := Sum[MoebiusMu[n/d]*BellB[d - 1], {d, Divisors[n]}];
Array[a, 23] (* Jean-François Alcover, Sep 08 2019 *)
PROG
(PARI)
bell(n) = sum(k=0, n, stirling(n, k, 2));
a(n) = sumdiv(n, d, moebius(n/d) * bell(d-1)); \\ Andrew Howroyd, Apr 03 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
More precise definition from Andrew Howroyd, Apr 03 2017
STATUS
approved