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Numbers n such that (2^n+n)/(n+2) is prime.
1

%I #6 Jun 13 2017 10:14:34

%S 13,19,55,469,3385

%N Numbers n such that (2^n+n)/(n+2) is prime.

%C All terms are also in A081765 = numbers n such that n+2 divides 2^(n-1)-1.

%t Do[If[PrimeQ[(2^n+n)/(n+2)],Print[n]],{n,1,5000}]

%o (PARI) is(n)=ispseudoprime((2^n+n)/(n+2)) \\ _Charles R Greathouse IV_, Jun 13 2017

%Y Cf. A081765.

%K more,nonn

%O 1,1

%A _Zak Seidov_, Sep 14 2006

%E a(5) from _Alexander Adamchuk_, Sep 17 2006