OFFSET
1,6
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..10000
FORMULA
If n = p^2 for some prime p then a(n) = p - 1 and a(k) <= a(n) for k <= n. - Peter Luschny, Sep 05 2023
MAPLE
with(numtheory): a := n -> add(phi(igcd(d, n/d)), d = factorset(n)); seq(a(n), n=1..100);
MATHEMATICA
a[n_] := Sum[EulerPhi[GCD[p, n/p]], {p, FactorInteger[n][[;; , 1]]}]; a[1] = 0; Array[a, 100] (* Amiram Eldar, Aug 29 2023 *)
PROG
(PARI) A240086(n) = sumdiv(n, p, (isprime(p)*eulerphi(gcd(p, n/p)))); \\ Antti Karttunen, Sep 23 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Peter Luschny, Mar 31 2014
EXTENSIONS
More terms from Antti Karttunen, Sep 23 2017
STATUS
approved