A050886 Numbers k such that 255*2^k-1 is prime.

1, 2, 3, 4, 6, 11, 12, 24, 40, 41, 61, 75, 86, 95, 158, 207, 223, 242, 276, 338, 390, 488, 673, 804, 1084, 1332, 1467, 1588, 2894, 3650, 4367, 6001, 6372, 10162, 10235, 10660, 12988, 17470, 18323, 18673, 24137, 24335, 24797, 28573, 35636, 36275, 44015

Offset

1,2

Links

Robert Price, Table of n, a(n) for n = 1..70

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[255*2^# - 1] & ] (* Robert Price, Dec 29 2018 *)

Prog

(PARI) is(n)=ispseudoprime(255*2^n-1) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Sequence in context: A084166 A245569 A018297 * A341652 A079310 A116853

Adjacent sequences: A050883 A050884 A050885 * A050887 A050888 A050889

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(48)-a(70) from the Wilfrid Keller link by Robert Price, Dec 29 2018

Status

approved