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A002269 Numbers k such that 39*2^k+1 is prime.
(Formerly M0640 N0234)
1
1, 2, 3, 5, 7, 10, 11, 13, 14, 18, 21, 22, 31, 42, 67, 70, 71, 73, 251, 370, 375, 389, 407, 518, 818, 865, 1057, 1602, 2211, 3049, 4802, 4865, 5317, 7583, 8061, 9853, 10217, 12103, 13721, 14927, 15441, 15931, 16709, 18907, 20221, 21882, 25654, 28437, 30325, 31485, 33593, 37393, 46362, 62429, 66971, 77242, 82191, 94449, 105063, 107778, 113490, 113549, 138009, 204681, 378861, 421590, 510595, 512997, 529642, 534973, 555902, 587850, 634441, 778233, 1612681, 1824871, 2188855 (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..77.

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

PROG

(PARI) is(n)=ispseudoprime(39*2^n+1) \\ Charles R Greathouse IV, Jun 06 2017

CROSSREFS

Sequence in context: A109608 A118241 A258613 * A047487 A048461 A058590

Adjacent sequences:  A002266 A002267 A002268 * A002270 A002271 A002272

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(77) from http://www.prothsearch.com/riesel1.html by Robert Price, Dec 14 2018

STATUS

approved

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Last modified March 18 19:58 EDT 2019. Contains 321293 sequences. (Running on oeis4.)