%I #4 Oct 02 2013 15:12:47

%S 1,4,5,6,20,22,25,46,47,214,822,985,3273,3590,4658,4768,17250,38697

%N Numbers n such that 3^n - phi(n) is prime.

%C Terms less than 1000 correspond to certified primes. Next term is greater than 10000.

%C a(19) > 10^5. [From _Donovan Johnson_, Feb 06 2010]

%t Do[If[PrimeQ[3^n - EulerPhi[n]], Print[n]], {n, 1, 10^4}]

%K hard,nonn

%O 1,2

%A _Ryan Propper_, Aug 31 2005

%E a(17)-a(18) from _Donovan Johnson_, Feb 06 2010