OFFSET
1,1
COMMENTS
What values of b can occur?
Apparently all even numbers can occur as values of b. Checked up to 50000; see A227533. - Charles R Greathouse IV, Jul 15 2013
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = A166955(n+2). - Juri-Stepan Gerasimov, Oct 25 2009
EXAMPLE
phi(63) = 6^2, phi(96) = 2^5.
MATHEMATICA
ppQ[n_] := GCD @@ Last /@ FactorInteger@ n > 1; Select[ Range@ 330, ppQ@ EulerPhi@ # &] (* Robert G. Wilson v, Jul 16 2013 *)
PROG
(PARI) v=[]; for(n=2, 333, if(ispower(eulerphi(n)), v=concat(v, n))); v (Hobson)
(PARI) is(n)=ispower(eulerphi(n)) \\ Charles R Greathouse IV, Jul 15 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Joseph L. Pe, Nov 27 2001
EXTENSIONS
More terms from Nick Hobson, Nov 29 2006
b-file from Charles R Greathouse IV, Mar 25 2010
STATUS
approved