OFFSET
1,9
COMMENTS
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..65537
FORMULA
Multiplicative with a(2^e) = 1, and for odd primes p, a(p^e) = p^(e-1).
Dirichlet g.f.: (1 - 1/(2^s-1)^2) * zeta(s-1) * Product_{p prime} (1 - 1/p^(s-1) + 1/p^s). - Amiram Eldar, Sep 14 2023
MATHEMATICA
f[2, e_] := 1; f[p_, e_] := p^(e-1); a[n_] := Times @@ (f @@@ FactorInteger[n]); Array[a, 100] (* Amiram Eldar, Dec 07 2020 *)
PROG
(PARI) A336651(n) = { my(f=factor(n)); prod(i=1, #f~, if(2==f[i, 1], 1, f[i, 1]^(f[i, 2]-1))); };
CROSSREFS
KEYWORD
nonn,easy,mult
AUTHOR
Antti Karttunen, Jul 30 2020
STATUS
approved