A323033 - OEIS

%I #14 Jan 18 2020 08:42:23

%S 3,15,17,20,21,41,44,51,113,140,179,219,249,323,461,521,671,680,692,

%T 695,716,809,825,887,897,1055,1439,1641,2873,4103,4593,6912,9551,

%U 13472,21131,23403,101225,104471,135993,163931,169824,182969,224085,273672,287543

%N Numbers k such that 381*2^k+1 is prime.

%H Jeppe Stig Nielsen, <a href="/A323033/b323033.txt">Table of n, a(n) for n = 1..57</a> (terms n = 1..55 from Robert Price)

%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/riesel1a.html">List of primes k.2^n + 1 for 300 < k < 600</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 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/ProthPrime.html">Proth Prime</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(381*2^k+1),[$1..1000]); # _Muniru A Asiru_, Jan 02 2019

%t Select[Range[1000], PrimeQ[381*2^# + 1] &] (* _Robert Price_, Jan 02 2019 *)

%K nonn,hard

%O 1,1

%A _Robert Price_, Jan 02 2019