%I #9 Feb 20 2022 20:26:16
%S 5,67,262153,1073741839,18889465931478580854821,
%T 1496577676626844588240573268701473812127674924007509,
%U 118571099379011784113736688648896417641748464297615937576404566024103044751294597
%N Primes of the form 4^k + k.
%C It is convenient, although not necessary, to let k be an odd number since k even => 4^k + k is even > 2.
%C Conjecture: sequence is infinite.
%C The next term (a(8)) has 126 digits. - _Harvey P. Dale_, Jun 05 2014
%e For k = 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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