OFFSET
1,2
COMMENTS
All powers of 2 are in the sequence.
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
MATHEMATICA
Select[Range[1100], !PrimeQ[#]&&PowerMod[#, 2, EulerPhi[#]]== PowerMod[ EulerPhi[ #], 2, #]&] (* Harvey P. Dale, Feb 07 2016 *)
PROG
(PARI) for(n=1, 2000, if(n^2%eulerphi(n)*(-1)^isprime(n)==eulerphi(n)^2%n, print1(n, ", ")))
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, May 14 2002
STATUS
approved