OFFSET
1,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..8299
FORMULA
a(n) = Sum_{k=1..n} phi(n/gcd(k, n))^gcd(k, n).
G.f.: Sum_{k>=1} phi(k)^2 * x^k/(1 - phi(k) * x^k).
If p is prime, a(p) = 1 + (p-1)^2 = A002522(p-1).
a(n) = Sum_{k=1..n} phi(gcd(k, n))^(n/gcd(k, n) + 1)/phi(n/gcd(k, n)). - Richard L. Ollerton, May 07 2021
MATHEMATICA
a[n_] := DivisorSum[n, EulerPhi[#]^(n/#+1) &]; Array[a, 50] (* Amiram Eldar, Mar 14 2021 *)
PROG
(PARI) a(n) = sumdiv(n, d, eulerphi(d)^(n/d+1));
(PARI) a(n) = sum(k=1, n, eulerphi(n/gcd(k, n))^gcd(k, n));
(PARI) my(N=66, x='x+O('x^N)); Vec(sum(k=1, N, eulerphi(k)^2*x^k/(1-eulerphi(k)*x^k)))
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Mar 13 2021
STATUS
approved