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%I #25 Jan 17 2019 10:08:17
%S 1,5,7,11,13,23,33,35,37,47,115,205,235,271,409,739,837,887,2189,3465,
%T 4653,5073,8011,8061,21957,24589,25657,44653,50321,57647,62083,78179,
%U 80021,81655,111667,150265,177089,196433,274115,306751,311389,315523,406105,421129
%N Numbers k such that 31*2^k-1 is prime.
%C 773227 is also in the sequence. - Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
%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 Kosmaj, <a href="http://www.15k.org/riesellist.html">Riesel list 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[31*2^# - 1] & ] (* _Robert Price_, Dec 22 2018 *)
%o (PARI) is(n)=ispseudoprime(31*2^n-1) \\ _Charles R Greathouse IV_, Jun 13 2017
%Y Cf. A032365 = 31*2^n+1 is prime.
%K nonn
%O 1,2
%A _N. J. A. Sloane_, Dec 29 1999
%E More terms from _Hugo Pfoertner_, Aug 29 2004
%E More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
%E a(43)-a(44) from the Wilfrid Keller link by _Robert Price_, Dec 22 2018