A112715 Primes in A112714.

3, 7, 11, 23, 31, 47, 79, 127, 191, 223, 239, 383, 479, 607, 863, 991, 1087, 1151, 1279, 1471, 1663, 2111, 2239, 2687, 2879, 3391, 3583, 3967, 5119, 5503, 6143, 6271, 6911, 7039, 8191, 8447, 8831, 9343, 10111, 11519, 11903, 12671, 12799, 13183, 13567

Offset: 1

Author

Jose Brox (tautocrona(AT)terra.es), Dec 31 2005

Keywords

• easy
• nonn

Examples

			a(1)=3 because 3=1*2^2-1 and it is the first prime of this form.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A080076.

Programs

Maple

N:= 10^6: # to get all terms <= N
sort(convert(select(isprime,{seq(seq(k*2^m-1,k=1..min((N+1)/2^m,2^m-1),2),m=1..ilog2(N+1))}),list)); # Robert Israel, May 23 2017

Mathematica

Take[Sort@ Select[Flatten@ Table[k 2^m - 1, {m, 0, 15}, {k, 1, 2^m - 1, 2}], PrimeQ], 45] (* Michael De Vlieger, May 23 2017, after Robert G. Wilson v at A112714 *)

PARI

for(n=2,8,for(k=2^(n-2)+1,2^n,M=k*2^n-1;if(isprime(M),print1(M","),0)))