A050523 Primes of the form 7*2^k - 1.

13, 223, 3583, 917503, 14680063, 3758096383, 246290604621823, 1340933598257652751063553648756520535666396731910651903

Offset: 1

Author

N. J. A. Sloane, Dec 29 1999

Keywords

• nonn
• nice

Links

• Index entries for sequences of n such that k*2^n-1 (or k*2^n+1) is prime.

Crossrefs

See A001771 for more terms.

Cf. A086224, A158795 [Vincenzo Librandi, Mar 28 2009]

Programs

Mathematica

Select[Table[7*2^n-1, {n,0,200}], PrimeQ] (* Jean-François Alcover, Mar 20 2011 *)

Formula

a(n) = A086224(A001771(n)). - Elmo R. Oliveira, Apr 22 2025

Extensions

13 inserted by R. J. Mathar, Apr 01 2009