%I #33 Dec 21 2024 03:28:21
%S 6,14,18,26,34,42,56,74,78,94,132,146,186,284,302,1758,1816,2336,3374,
%T 3466,4522,8058,11114,12456,22172,26208,39794,61512,81576,238734,
%U 270794,348972,420034,680694,682974,964444,1076024,1124806,1158186,1786968,2082202
%N Numbers k such that 247*2^k+1 is prime.
%H Jeppe Stig Nielsen, <a href="/A032500/b032500.txt">Table of n, a(n) for n = 1..44</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[247*2^# + 1] & ] (* _Robert Price_, Dec 20 2018 *)
%o (PARI) is(n)=ispseudoprime(247*2^n+1) \\ _Charles R Greathouse IV_, Jun 13 2017
%K nonn,hard
%O 1,1
%A _N. J. A. Sloane_.
%E a(30)-a(40) from the Ray Ballinger and Wilfrid Keller link by _Robert Price_, Dec 20 2018
%E a(41) from _Jeppe Stig Nielsen_, Jan 19 2020