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A129963 Primes of the form 4^n + n. 2

%I

%S 5,67,262153,1073741839,18889465931478580854821,

%T 1496577676626844588240573268701473812127674924007509,

%U 118571099379011784113736688648896417641748464297615937576404566024103044751294597

%N Primes of the form 4^n + n.

%C It is convenient, although not necessary, to let n be an odd number since n even => 4^n + n is even > 2. Conjecture: There is an infinite number of primes in this sequence.

%C The next term (a(8)) has 126 digits. - _Harvey P. Dale_, Jun 05 2014

%e For n = 3, 4^3+3=67 is prime.

%t Select[Table[4^n+n,{n,1,251,2}],PrimeQ] (* _Harvey P. Dale_, Jun 05 2014 *)

%o (PARI) f(n) = for(x=1,n,y=2^x+x;if(isprime(y),print1(y",")))

%K nonn

%O 1,1

%A _Cino Hilliard_, Jun 10 2007, Aug 20 2007

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Last modified December 5 09:15 EST 2016. Contains 278762 sequences.