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

0,1

Links

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

Example

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.

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 *)

Crossrefs

Cf. A056206.

Sequence in context: A126116 A161423 A133846 * A323065 A225421 A175235

Adjacent sequences: A056205 A056206 A056207 * A056209 A056210 A056211

Keyword

nonn

Author

Labos Elemer, Oct 06 2000

Extensions

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

Status

approved