A050848 Numbers k such that 193*2^k-1 is prime.

3, 15, 27, 63, 87, 135, 543, 1383, 1455, 7767, 18543, 22143, 40967, 198719, 405483, 439107, 880287

Offset

1,1

Links

Table of n, a(n) for n=1..17.

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[193*2^# - 1] & ] (* Robert Price, Dec 29 2018 *)

Prog

(PARI) is(n)=ispseudoprime(193*2^n-1) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Sequence in context: A147041 A347536 A002259 * A077785 A222291 A015646

Adjacent sequences: A050845 A050846 A050847 * A050849 A050850 A050851

Keyword

hard,nonn,more

Author

N. J. A. Sloane, Dec 29 1999

Extensions

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

a(17) from the Wilfrid Keller link by Robert Price, Dec 29 2018

Status

approved