A050565 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give

A050565

Numbers k such that 79*2^k-1 is prime.

0

1, 3, 7, 15, 43, 57, 61, 75, 145, 217, 247, 2803, 3403, 4375, 5113, 9883, 14565, 17397, 65977, 82081, 92517, 214453, 248055, 369535, 969795

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Table of n, a(n) for n=1..25.

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

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

Kosmaj, Riesel list k<300.

MATHEMATICA

Select[Range[1000], PrimeQ[79*2^# - 1] & ] (* Robert Price, Dec 22 2018 *)

PROG

(PARI) is(n)=ispseudoprime(79*2^n-1) \\ Charles R Greathouse IV, Jun 13 2017

CROSSREFS

Sequence in context: A230958 A146033 A147188 * A097111 A371914 A151401

Adjacent sequences: A050562 A050563 A050564 * A050566 A050567 A050568

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(25) from the Wilfrid Keller link by Robert Price, Dec 22 2018

STATUS

approved