OFFSET
1,1
COMMENTS
It is obvious that all terms are primes. There is no further term up to 5*10^9.
MATHEMATICA
Do[If[n=Prime[m]; m==EulerPhi[DivisorSigma[1, PrimePi[n]]], Print[n]], {m, 235000000}]
CROSSREFS
KEYWORD
more,nonn
AUTHOR
Farideh Firoozbakht, Aug 04 2009
STATUS
approved