A056208 Primes p+2^n arising in A056206.

3, 5, 7, 11, 19, 37, 67, 131, 263, 523, 1031, 2053, 4099, 8209, 16421, 32771, 65539, 131101, 262147, 524341, 1048583, 2097169, 4194371, 8388619, 16777259, 33554473, 67108961, 134217757, 268435459, 536870923, 1073741827, 2147483659

Offset: 0

Author

Labos Elemer, Oct 06 2000

Keywords

• nonn

Examples

			n=13, 2^13+p=8192+p is not prime for p=2,3,5,7,11,13. At first, for p=17, 8209 is prime; Primes obtained also for many larger p, the next is 8221. So a(13)=8209, the smallest one.
		

Links

• Robert Israel, Table of n, a(n) for n = 0..2000

Crossrefs

Cf. A056206.

Programs

Maple

f:= proc(n) local p,q,t;
  t:= 2^n; p:= 1;
  do
    p:= nextprime(p);
    q:= p+t;
    if isprime(q) then return q fi
  od
end proc:
map(f, [$0..50]); # Robert Israel, Aug 22 2019

Mathematica

a[n_] := Module[{p = 1, q, t = 2^n}, While[True, p = NextPrime[p]; q = p+t; If[PrimeQ[q], Return[q]]]];
a /@ Range[0, 50] (* Jean-François Alcover, Jun 09 2020, after Maple *)

Extensions

a(0)=3 inserted by Robert Israel, Aug 22 2019