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Numbers k such that 191*2^k+1 is prime.
1

%I #36 Apr 04 2020 21:38:20

%S 1,5,15,19,41,59,89,149,167,181,201,295,475,481,857,1249,1409,1715,

%T 1995,8291,11031,26219,38029,39155,61747,73855,168707,180559,266997,

%U 366215,449381,552085,585377,903061,1099867,1487775,1496507,1567005,1766221,1916611

%N Numbers k such that 191*2^k+1 is prime.

%C The subsequence of prime values starts 5, 19, 41, 59, 89, 149, 167, 181, 857, 1249, 1409, 8291, 449381, 1099867, 1496507, 1916611, ... - _Muniru A Asiru_, Apr 20 2019

%H Jeppe Stig Nielsen, <a href="/A032472/b032472.txt">Table of n, a(n) for n = 1..41</a>

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

%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>

%p select(k->isprime(191*2^k+1),[$0..1000]); # _Muniru A Asiru_, Dec 18 2018

%t Select[Range[1000], PrimeQ[191*2^# + 1] & ] (* _Robert Price_, Dec 18 2018 *)

%o (PARI) is(n)=ispseudoprime(191*2^n+1) \\ _Charles R Greathouse IV_, Jun 07 2017

%K nonn,hard

%O 1,2

%A _N. J. A. Sloane_

%E a(27)-a(40) from the Ray Ballinger and Wilfrid Keller link by _Robert Price_, Dec 18 2018