OFFSET
1,2
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
EXAMPLE
a(1)=1 (phi(1)=1^1); a(2)=2 (phi(2)=1^1); a(3)=5 (phi(5)=2^2).
MATHEMATICA
ppQ[n_] := GCD @@ Last /@ FactorInteger@ n > 1; ppQ[1] = True; Select[ Range@ 330, ppQ[ EulerPhi[ #]] &] (* Robert G. Wilson v, Dec 12 2012 *)
PROG
(PARI) v=[1, 2]; for(n=3, 320, if(ispower(eulerphi(n)), v=concat(v, n))); v (Hobson)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Juri-Stepan Gerasimov, Oct 25 2009
EXTENSIONS
b-file from Charles R Greathouse IV, Mar 25 2010
STATUS
approved