OFFSET
1,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..388
FORMULA
a(n) = Sum_{d|n} phi(n/d) * phi(d)^n.
If p is prime, a(p) = p-1 + (p-1)^p.
a(n) = Sum_{k=1..n} phi(n/gcd(n,k))^(n-1)*phi(gcd(n,k)). - Richard L. Ollerton, May 09 2021
MATHEMATICA
a[n_] := DivisorSum[n, EulerPhi[n/#] * EulerPhi[#]^n &]; Array[a, 20] (* Amiram Eldar, Mar 15 2021 *)
PROG
(PARI) a(n) = sum(k=1, n, eulerphi(gcd(k, n))^n);
(PARI) a(n) = sumdiv(n, d, eulerphi(n/d)*eulerphi(d)^n);
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Mar 15 2021
STATUS
approved