%I #30 Apr 04 2020 21:43:29

%S 1,5,7,17,25,35,67,281,331,491,581,941,1205,1279,1411,1631,1895,2735,

%T 3475,13955,50491,68819,423155,432719,507637,701981,924085,1107425,

%U 2071555,2369461

%N Numbers k such that 125*2^k+1 is prime.

%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 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 <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[125*2^# + 1] & ] (* _Robert Price_, Dec 17 2018 *)

%o (PARI) is(n)=ispseudoprime(125*2^n+1) \\ _Charles R Greathouse IV_, Jun 13 2017

%K nonn,more

%O 1,2

%A _James R. Buddenhagen_

%E a(23)-a(29) from the Ray Ballinger and Wilfrid Keller link by _Robert Price_, Dec 17 2018

%E a(30) from _Jeppe Stig Nielsen_, Apr 04 2020