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%I #26 Sep 08 2022 08:45:00
%S 7,15,21,25,27,69,71,105,207,285,611,635,647,969,1127,1159,2407,2529,
%T 3517,3577,6275,6729,7919,8809,9375,27369,31657,44149,58579,59355,
%U 274255,285435,350949,485505,821221,834297
%N Numbers k such that 275*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[5*10^3], PrimeQ[275*2^# + 1] &] (* _G. C. Greubel_, May 24 2018 *)
%o (PARI) is(n)=ispseudoprime(275*2^n+1) \\ _Charles R Greathouse IV_, Jun 13 2017
%o (Magma) [n: n in [1..300] | IsPrime(275*2^n+1)]; // _G. C. Greubel_, May 24 2018
%K hard,nonn,more
%O 1,1
%A _N. J. A. Sloane_, Dec 29 1999
%E a(31)-a(36) from the Ray Ballinger and Wilfrid Keller link by _Robert Price_, Dec 20 2018
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