OFFSET
1,6
COMMENTS
A signed version of A050328.
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..10000
FORMULA
a(1) = 1; a(n) = Sum_{d|n, d < n} mu(n/d) * a(d). - Ilya Gutkovskiy, Feb 23 2020
MATHEMATICA
a050328[n_]:=If[n==1, n, Sum[If[(d<n && SquareFreeQ[n/d]), a050328[d], 0], {d, Divisors[n]}]]; a[n_]:=(-1)^PrimeOmega[n]*a050328[n]; Table[a[n], {n, 100}] (* Indranil Ghosh, May 27 2017 *)
PROG
(PARI)
CROSSREFS
KEYWORD
easy,sign
AUTHOR
Paul Barry, Nov 12 2005
EXTENSIONS
More terms, incorrect formulas replaced by a correct one - Antti Karttunen, May 27 2017
STATUS
approved