OFFSET
1,6
LINKS
FORMULA
a(1) = 1, and for n > 1, a(n) = -Sum_{d|n, d<n} A091862(n/d) * a(d).
MATHEMATICA
s[n_] := If[n == 1 || PrimeOmega[n] == BitOr @@ FactorInteger[n][[;; , 2]], 1, 0]; a[1] = 1; a[n_] := a[n] = -DivisorSum[n, s[n/#]*a[#] &, # < n &]; Array[a, 100] (* Amiram Eldar, Jul 21 2022 *)
PROG
CROSSREFS
KEYWORD
sign
AUTHOR
Antti Karttunen, Jul 21 2022
STATUS
approved