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A002261 Numbers k such that 11*2^k + 1 is prime.
(Formerly M2425 N0960)
4

%I M2425 N0960 #41 Oct 14 2023 21:10:25

%S 1,3,5,7,19,21,43,81,125,127,209,211,3225,4543,10179,15329,18759,

%T 28277,93279,105741,268009,412447,525589,644677,886071,960901,1343347,

%U 2230369,2476839,2691961,2897409,3771821

%N Numbers k such that 11*2^k + 1 is prime.

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

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

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

%H Ray Ballinger, <a href="http://www.prothsearch.com/index.html">Proth Search Page</a>.

%H Ray Ballinger and Wilfrid Keller, <a href="http://www.prothsearch.com/riesel1.html">List of primes k.2^n + 1 for k < 300</a>.

%H Y. Gallot, <a href="http://www.utm.edu/research/primes/programs/gallot/index.html">Proth.exe: Windows Program for Finding Large Primes</a>.

%H Wilfrid Keller, <a href="http://www.prothsearch.com/riesel2.html">List of primes k.2^n - 1 for k < 300</a>.

%H R. M. Robinson, <a href="https://doi.org/10.1090/S0002-9939-1958-0096614-7">A report on primes of the form k.2^n+1 and on factors of Fermat numbers</a>, Proc. Amer. Math. Soc., 9 (1958), 673-681.

%H <a href="/index/Pri#riesel">Index entries for sequences of n such that k*2^n-1 (or k*2^n+1) is prime</a>

%t Select[Range[1000], PrimeQ[11*2^#+1] &] (* _Amiram Eldar_, Dec 12 2018 *)

%o (PARI) is(n)=ispseudoprime(11*2^n+1) \\ _Charles R Greathouse IV_, Feb 20 2017

%K hard,nonn

%O 1,2

%A _N. J. A. Sloane_

%E Added more terms (from http://web.archive.org/web/20161028080239/http://www.prothsearch.net/riesel.html), _Joerg Arndt_, Apr 07 2013

%E a(30)-a(32) from http://www.prothsearch.com/riesel1.html by _Robert Price_, Dec 12 2018

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Last modified March 29 03:51 EDT 2024. Contains 371264 sequences. (Running on oeis4.)