OFFSET
1,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = Sum_{k=1..n} phi(gcd(n,k) + 1)/phi(n/gcd(n,k)). - Richard L. Ollerton, May 09 2021
MATHEMATICA
A069949[n_]:= DivisorSum[n, EulerPhi[#+1] &];
Table[A069949[n], {n, 100}] (* G. C. Greubel, Jun 24 2024 *)
PROG
(PARI) a(n)=sumdiv(n, d, eulerphi(d+1) ); /* Joerg Arndt, Sep 30 2012 */
(Magma)
A069949:= func< n | (&+[EulerPhi(d+1): d in Divisors(n)]) >;
[A069949(n): n in [1..100]]; // G. C. Greubel, Jun 24 2024
(SageMath)
def A069949(n): return sum(euler_phi(k+1) for k in (1..n) if (k).divides(n))
[A069949(n) for n in range(1, 101)] # G. C. Greubel, Jun 24 2024
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladeta Jovovic, May 04 2002
STATUS
approved