%I
%S 2,5,7,13,19,37,59,67,79,307,331,599,1301,12263,12589,18443,20149,
%T 27983
%N Numbers k such that (5^k  2^k)/3 is prime.
%C No other terms less than 100000.  _Robert Price_, Apr 06 2012
%C All terms are primes. Some of the results were computed using the PrimeFormGW (PFGW) primalitytesting program.  _Hugo Pfoertner_, Nov 14 2019
%H OEIS Wiki, <a href="http://oeis.org/wiki/Primes_of_the_form_(a%5En%2Bb%5En)/(a%2Bb)_and_(a%5Enb%5En)/(ab)">Primes of the form (a^n+b^n)/(a+b) and (a^nb^n)/(ab)</a>.
%e Example: a(1)=2 because (5^2  2^2)/3 = (25  4)/3 = 7 is a prime.
%t a={};Do[p=(5^n2^n)/3;If[PrimeQ[p],AppendTo[a,n]],{n,20^2}];Print[a]; (* _Vladimir Joseph Stephan Orlovsky_, Apr 29 2008 *)
%o (PARI) forprime(p=2,1e4,if(ispseudoprime((5^p2^p)/3),print1(p", "))) \\ _Charles R Greathouse IV_, Jul 16, 2011
%K more,nonn
%O 1,1
%A _Hugo Pfoertner_, May 22 2003, Jun 23 2003
%E 20149 from Herman Jamke (hermanjamke(AT)fastmail.fm), May 03 2007
%E 27983 from _David Radcliffe_, May 28 2007
