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

1,2

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

Essentially the same as A065528.

Sequence in context: A237525 A290578 A294127 * A286808 A121294 A039770

Adjacent sequences: A166952 A166953 A166954 * A166956 A166957 A166958

Keyword

nonn,easy

Author

Juri-Stepan Gerasimov, Oct 25 2009

Extensions

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

Status

approved