A166955 - OEIS

%I #9 May 13 2013 01:54:10

%S 1,2,5,8,10,12,15,16,17,20,24,30,32,34,37,40,48,51,57,60,63,64,68,74,

%T 76,80,85,96,101,102,108,114,120,125,126,128,136,160,170,185,192,197,

%U 202,204,219,240,247,250,255,256,257,259,272,273,285,292,296,304,315,320,327

%N phi(n) is a perfect power.

%H Charles R Greathouse IV, <a href="/A166955/b166955.txt">Table of n, a(n) for n = 1..10000</a>

%e a(1)=1 (phi(1)=1^1); a(2)=2 (phi(2)=1^1); a(3)=5 (phi(5)=2^2).

%t ppQ[n_] := GCD @@ Last /@ FactorInteger@ n > 1; ppQ[1] = True; Select[ Range@ 330, ppQ[ EulerPhi[ #]] &] (* _Robert G. Wilson v_, Dec 12 2012 *)

%o (PARI) v=[1,2]; for(n=3, 320, if(ispower(eulerphi(n)), v=concat(v,n))); v (Hobson)

%Y Essentially the same as A065528.

%K nonn,easy

%O 1,2

%A _Juri-Stepan Gerasimov_, Oct 25 2009

%E b-file from _Charles R Greathouse IV_, Mar 25 2010