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%I M2670 #34 Dec 26 2021 22:09:29
%S 3,7,19,31,41,2687,19697,59693,67421,441697
%N Numbers k such that (14^k - 1)/13 is prime.
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H Paul Bourdelais, <a href="https://listserv.nodak.edu/cgi-bin/wa.exe?A2=NMBRTHRY;417ab0d6.0906">A Generalized Repunit Conjecture</a>
%H H. Dubner, <a href="http://dx.doi.org/10.1090/S0025-5718-1993-1185243-9">Generalized repunit primes</a>, Math. Comp., 61 (1993), 927-930.
%H H. Dubner, <a href="/A028491/a028491.pdf">Generalized repunit primes</a>, Math. Comp., 61 (1993), 927-930. [Annotated scanned copy]
%H H. Lifchitz, <a href="http://www.primenumbers.net/Henri/us/MersFermus.htm">Mersenne and Fermat primes field</a>
%t lst={};Do[If[PrimeQ[(14^n-1)/13], Print[n];AppendTo[lst, n]], {n, 10^5}];lst (* _Vladimir Joseph Stephan Orlovsky_, Aug 21 2008 *)
%o (PARI) is(n)=isprime((14^n - 1)/13) \\ _Charles R Greathouse IV_, Apr 29 2015
%K hard,nonn,more
%O 1,1
%A _N. J. A. Sloane_
%E One more term from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 05 2008
%E a(8) and a(9) correspond to probable primes discovered by _Paul Bourdelais_, Mar 01 2010
%E a(10) corresponds to a probable prime discovered by _Paul Bourdelais_, Dec 08 2014
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