A002258 Numbers k such that 15*2^k + 1 is prime. (Formerly M1165 N0445)

1, 2, 4, 9, 10, 12, 27, 37, 38, 44, 48, 78, 112, 168, 229, 297, 339, 517, 522, 654, 900, 1518, 2808, 2875, 3128, 3888, 4410, 6804, 7050, 7392, 19219, 21445, 21550, 24105, 24995, 34224, 34260, 43388, 48444, 61758, 184290, 294894, 300488, 403929, 483098, 635989

Offset

1,2

References

H. Riesel, "Prime numbers and computer methods for factorization," Progress in Mathematics, Vol. 57, Birkhauser, Boston, 1985, Chap. 4, see pp. 381-384.

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

Jeppe Stig Nielsen, Table of n, a(n) for n = 1..63

Ray Ballinger, Proth Search Page

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

Y. Gallot, Proth.exe: Windows Program for Finding Large Primes

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

R. M. Robinson, A report on primes of the form k.2^n+1 and on factors of Fermat numbers, Proc. Amer. Math. Soc., 9 (1958), 673-681.

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

Mathematica

Select[Range[1000], PrimeQ[15*2^#+1] &] (* Amiram Eldar, Dec 12 2018 *)

Prog

(PARI) for(n=1, 10^10, if(ispseudoprime(15<<n+1), print1(n, ", "))); \\ Joerg Arndt, Feb 23 2014

Crossrefs

Sequence in context: A226821 A047465 A365343 * A252760 A191766 A287518

Adjacent sequences: A002255 A002256 A002257 * A002259 A002260 A002261

Keyword

hard,nonn

Author

N. J. A. Sloane

Extensions

Added more terms (from http://web.archive.org/web/20161028080239/http://www.prothsearch.net/riesel.html), Joerg Arndt, Apr 07 2013

a(57)-a(60) from http://www.prothsearch.com/riesel1.html by Robert Price, Dec 12 2018

Terms moved from Data to b-file, and one new term put in b-file, by Jeppe Stig Nielsen, Oct 16 2019

Status

approved