A050849 Numbers k such that 195*2^k-1 is prime.

1, 3, 4, 6, 8, 9, 10, 14, 23, 26, 28, 35, 44, 46, 50, 55, 60, 63, 65, 78, 99, 100, 106, 111, 163, 178, 180, 364, 569, 825, 838, 958, 1292, 1425, 1531, 2020, 2259, 2434, 2492, 2520, 3310, 3624, 4195, 4206, 5103, 5139, 5478, 7198, 7335, 8123, 9903, 12239

Offset

1,2

Links

Robert Price, Table of n, a(n) for n = 1..75

Ray Ballinger and Wilfrid Keller, List of primes k.2^n + 1 for k < 300

Wilfrid Keller, List of primes k.2^n - 1 for k < 300

Kosmaj, Riesel list k<300.

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

Mathematica

Select[Range[1000], PrimeQ[195*2^# - 1] & ] (* Robert Price, Dec 29 2018 *)

Prog

(PARI) is(n)=ispseudoprime(195*2^n-1) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Sequence in context: A062969 A175035 A025063 * A039008 A291322 A322741

Adjacent sequences: A050846 A050847 A050848 * A050850 A050851 A050852

Keyword

hard,nonn

Author

N. J. A. Sloane, Dec 29 1999

Extensions

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008

a(53)-a(75) from the Wilfrid Keller link by Robert Price, Dec 29 2018

Status

approved