A032503 - OEIS

%I #33 Jul 08 2025 19:41:03

%S 2,4,6,16,32,48,50,52,64,66,72,86,108,130,164,304,356,482,486,712,772,

%T 834,1196,1508,1552,1600,1754,1858,2228,3562,3900,4834,10400,26736,

%U 33700,34276,35860,38152,61256,76828,169312,186218,204140,335828,483768,485188

%N Numbers k such that 253*2^k+1 is prime.

%H Jeppe Stig Nielsen, <a href="/A032503/b032503.txt">Table of n, a(n) for n = 1..54</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>

%t Select[Range[1000], PrimeQ[253*2^# + 1] & ] (* _Robert Price_, Dec 20 2018 *)

%o (PARI) is(n)=ispseudoprime(253*2^n+1) \\ _Charles R Greathouse IV_, Jun 13 2017

%K nonn,hard

%O 1,1

%A _N. J. A. Sloane_

%E a(35)-a(51) from the Ray Ballinger and Wilfrid Keller link by _Robert Price_, Dec 20 2018

%E Terms moved from Data section to b-file, and more terms added to b-file by _Jeppe Stig Nielsen_, Mar 12 2020