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%I #32 Apr 04 2020 19:21:41
%S 13,25,29,33,45,57,65,153,197,245,637,1785,1917,2045,4925,5313,7449,
%T 8437,23645,28273,34217,40189,135125,141477,169077,215945,234229,
%U 265089,482177,556069,1335989,1357425,1966689,2526505
%N Numbers k such that 203*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[0, 1000], PrimeQ[203*2^# + 1] &] (* _Robert Price_, Dec 09 2018 *)
%o (PARI) is(n)=ispseudoprime(203*2^n+1) \\ _Charles R Greathouse IV_, Jun 13 2017
%K nonn,hard
%O 1,1
%A _N. J. A. Sloane_
%E a(25)-a(32) from Ray Ballinger and Wilfrid Keller link by _Robert Price_, Dec 09 2018
%E a(33) from updated Ray Ballinger and Wilfrid Keller link by _Robert Price_, Dec 10 2018
%E a(34) from _Jeppe Stig Nielsen_, Apr 04 2020
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