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%I #26 Apr 20 2020 02:20:37
%S 15,19,35,55,59,115,163,371,1175,3047,5615,7855,9155,16467,22303,
%T 32879,66123,70619,85607,117047,238083,354335,1502095,1568755,1830255,
%U 2244347
%N Numbers k such that 197*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 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[197*2^# + 1] & ] (* _Robert Price_, Dec 19 2018 *)
%o (PARI) is(n)=ispseudoprime(197*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_, Apr 19 2020
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