A166955 phi(n) is a perfect power.

1, 2, 5, 8, 10, 12, 15, 16, 17, 20, 24, 30, 32, 34, 37, 40, 48, 51, 57, 60, 63, 64, 68, 74, 76, 80, 85, 96, 101, 102, 108, 114, 120, 125, 126, 128, 136, 160, 170, 185, 192, 197, 202, 204, 219, 240, 247, 250, 255, 256, 257, 259, 272, 273, 285, 292, 296, 304, 315, 320, 327

Offset: 1

Author

Juri-Stepan Gerasimov, Oct 25 2009

Keywords

• nonn
• easy

Examples

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

Links

• Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Crossrefs

Essentially the same as A065528.

Programs

Mathematica

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

PARI

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

Extensions

b-file from Charles R Greathouse IV, Mar 25 2010