OFFSET
1,2
COMMENTS
As phi(2^(5*n+1)) = (2^n)^5, A013822 is a subsequence. - Bernard Schott, Sep 26 2022
Numbers of the form u = 2^(5*k)*3^(5*m + 1), k>=1, m>=0, are terms because phi(u) = 2^(5*k)*3^(5*m) = (2^k*3^m)^5. - Marius A. Burtea, Sep 26 2022
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
phi of the sequence includes 1, 32, 1024, 7776, ...; powers arise several times; a(3) = A053576(5) = 51.
MATHEMATICA
k=5; Do[s=EulerPhi[n]^(1/k); If[IntegerQ[s], Print[n]], {n, 1, 5000}]
Select[Range[15000], IntegerQ[Surd[EulerPhi[#], 5]]&] (* Harvey P. Dale, Jul 26 2019 *)
PROG
(PARI) is(n)=ispower(eulerphi(n), 5) \\ Charles R Greathouse IV, Apr 24 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Nov 27 2002
STATUS
approved