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%I M5072 #35 Sep 10 2018 13:29:03
%S 19,31,47,59,61,107,337,1061,9511,22051,209359
%N Numbers n such that (19^n-1)/18 is prime.
%C No others less than 8011. - Julien Peter Benney (jpbenney(AT)ftml.net), Aug 15 2004
%C a(9) = 9511 was found by Richard Fischer on Dec 15 2004. - _Alexander Adamchuk_, Feb 11 2007
%D Ribenboim, Paulo; "The Book Of Prime Number Records"; published 1989 by Springer-Verlag; pages 350-354.
%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>. - _Paul Bourdelais_, Aug 27 2010
%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>
%H <a href="/index/Pri#primepop">Index to primes in various ranges</a>, form ((k+1)^n-1)/k
%t lst={};Do[If[PrimeQ[(19^n-1)/18], Print[n];AppendTo[lst, n]], {n, 10^5}];lst (* _Vladimir Joseph Stephan Orlovsky_, Aug 21 2008 *)
%o (PARI) is(n)=isprime((19^n-1)/18) \\ _Charles R Greathouse IV_, Apr 28 2015
%K 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(11)=209359 corresponds to a probable prime discovered by _Paul Bourdelais_, Aug 27 2010
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