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A002261 Numbers k such that 11*2^k+1 is prime.
(Formerly M2425 N0960)
4
1, 3, 5, 7, 19, 21, 43, 81, 125, 127, 209, 211, 3225, 4543, 10179, 15329, 18759, 28277, 93279, 105741, 268009, 412447, 525589, 644677, 886071, 960901, 1343347, 2230369, 2476839, 2691961, 2897409, 3771821 (list; graph; refs; listen; history; text; internal format)
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

Table of n, a(n) for n=1..32.

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[11*2^#+1] &] (* Amiram Eldar, Dec 12 2018 *)

PROG

(PARI) is(n)=ispseudoprime(11*2^n+1) \\ Charles R Greathouse IV, Feb 20 2017

CROSSREFS

Sequence in context: A112986 A052333 A074106 * A263257 A261456 A154524

Adjacent sequences:  A002258 A002259 A002260 * A002262 A002263 A002264

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(30)-a(32) from http://www.prothsearch.com/riesel1.html by Robert Price, Dec 12 2018

STATUS

approved

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Last modified November 29 14:23 EST 2020. Contains 338769 sequences. (Running on oeis4.)