A104066 Primes of the form 2^k + 7.

11, 23, 71, 263, 1031, 65543, 262151, 1048583, 268435463, 1073741831, 274877906951, 17592186044423, 302231454903657293676551, 309485009821345068724781063, 316912650057057350374175801351

Offset: 1

Author

Roger L. Bagula, Mar 02 2005

Keywords

• nonn

Comments

Also primes of the form 4^n+7 (in this case, the associated n are in A217349). - Bruno Berselli, Oct 03 2012

Crossrefs

Cf. A000040, A057195 (numbers k such that 2^k + 7 is prime).

Programs

Magma

[a: n in [0..100 by 2] | IsPrime(a) where a is 2^n+7]; // Vincenzo Librandi, Jan 26 2011

Mathematica

a = Delete[Union[Flatten[Table[If [PrimeQ[2^n + 7] == True, 2^ n + 7, 0], {n, 1, 400}]]], 1]

PARI

list(lim)=my(v=List(),t); for(n=1,logint(lim\1-7,4), if(ispseudoprime(t=4^n+7), listput(v,t))); Vec(v) \\ Charles R Greathouse IV, Nov 17 2017

Formula

a(n) = 2^A057195(n) + 7. - Elmo R. Oliveira, Nov 08 2023