%I #33 Dec 21 2024 06:15:59
%S 11,15,35,51,83,87,99,183,4619,4659,6939,7503,10647,13007,18459,19599,
%T 26363,43719,53171,140679,249599,308139,797603,1542323,1786779,5213195
%N Numbers k such that 227*2^k+1 is prime.
%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[227*2^# + 1] & ] (* _Robert Price_, Dec 19 2018 *)
%o (PARI) is(n)=ispseudoprime(227*2^n+1) \\ _Charles R Greathouse IV_, Jun 13 2017
%K nonn,hard,more
%O 1,1
%A _N. J. A. Sloane_.
%E a(20)-a(25) from the Ray Ballinger and Wilfrid Keller link by _Robert Price_, Dec 19 2018
%E a(26) from _Jeppe Stig Nielsen_, Dec 21 2024