

A129963


Primes of the form 4^n + n.


2



5, 67, 262153, 1073741839, 18889465931478580854821, 1496577676626844588240573268701473812127674924007509, 118571099379011784113736688648896417641748464297615937576404566024103044751294597
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OFFSET

1,1


COMMENTS

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.
The next term (a(8)) has 126 digits.  Harvey P. Dale, Jun 05 2014


LINKS

Table of n, a(n) for n=1..7.


EXAMPLE

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


MATHEMATICA

Select[Table[4^n+n, {n, 1, 251, 2}], PrimeQ] (* Harvey P. Dale, Jun 05 2014 *)


PROG

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


CROSSREFS

Sequence in context: A197776 A197606 A207979 * A115764 A252794 A003361
Adjacent sequences: A129960 A129961 A129962 * A129964 A129965 A129966


KEYWORD

nonn


AUTHOR

Cino Hilliard, Jun 10 2007, Aug 20 2007


STATUS

approved



