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Numbers n such that 4^n - n is prime.
4

%I #12 Jan 07 2015 18:14:58

%S 1,3,5,35,95,1323,24747

%N Numbers n such that 4^n - n is prime.

%C a(8) > 2*10^5. - _Robert Price_, Feb 11 2014

%t Do[ If[ PrimeQ[ 4^n - n ], Print[ n ] ], {n, 0, 3000} ]

%o (PARI) for(k=1,10^6,if(ispseudoprime(4^k-k),print1(k,", "))); /* _Joerg Arndt_, Apr 07 2013 */

%K nonn,more

%O 1,2

%A _Robert G. Wilson v_, Nov 16 2000

%E a(7) from _Robert Price_, Feb 11 2014