A077314 Primes of the form 2^r*7^s - 1.

3, 7, 13, 31, 97, 127, 223, 1567, 3583, 4801, 6271, 8191, 19207, 25087, 33613, 76831, 131071, 401407, 524287, 917503, 1229311, 1605631, 3764767, 6588343, 14680063, 184473631, 737894527, 2147483647, 2259801991, 2877292543, 3758096383

Offset: 1

Author

Amarnath Murthy, Nov 04 2002

Keywords

• nonn

Comments

In all terms except 3, r is odd. - Robert Israel, Jun 08 2018

Links

• Robert Israel, Table of n, a(n) for n = 1..1736

Crossrefs

Cf. A023509, A077313.

Programs

Maple

N:= 10^30: # for all terms <= N
sort(select(isprime, [3, seq(seq(2^r*7^s-1, r=1..ilog2((N+1)/7^s),2),
s=0..floor(log[7]((N+1)/2)))])); # Robert Israel, Jun 08 2018

Extensions

Corrected and extended by Ray Chandler, Aug 02 2003