OFFSET
1,9
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..20000
FORMULA
MATHEMATICA
f[p_, e_] := -(p - 1)^(e - 1); a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 100] (* Amiram Eldar, Nov 18 2021 *)
PROG
(PARI)
A003557(n) = (n/factorback(factorint(n)[, 1]));
memoA349340 = Map();
A349340(n) = if(1==n, 1, my(v); if(mapisdefined(memoA349340, n, &v), v, v = -sumdiv(n, d, if(d<n, A003557(n/d)*A349340(d), 0)); mapput(memoA349340, n, v); (v)));
(PARI) A349340(n) = { my(f=factor(n)); prod(i=1, #f~, -((f[i, 1]-1)^(f[i, 2]-1))); };
CROSSREFS
KEYWORD
sign,mult
AUTHOR
Antti Karttunen, Nov 18 2021
STATUS
approved