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 A057180 Numbers n such that (14^n + 1)/15 is a prime. 15
 7, 53, 503, 1229, 22637, 1091401 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Of the Repunit primes with base -21<=b<=21, base=-14 is the most "unlucky" with a normalized prime occurrence rate of 0.86289. The Generalized Repunit Conjecture (see below) states that this will eventually improve and converge to Euler's Constant (~0.55). - Paul Bourdelais, Mar 10 2014 LINKS Paul Bourdelais, A Generalized Repunit Conjecture J. Brillhart et al., Factorizations of b^n +- 1, Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 3rd edition, 2002. H. Dubner and T. Granlund, Primes of the Form (b^n+1)/(b+1), J. Integer Sequences, 3 (2000), #P00.2.7. H. Lifchitz, Mersenne and Fermat primes field PROG (Prime95) PRP=1, 14, 1091401, 1, 0, 0, "15" CROSSREFS Sequence in context: A081338 A142981 A120272 * A137612 A092802 A062207 Adjacent sequences:  A057177 A057178 A057179 * A057181 A057182 A057183 KEYWORD nonn AUTHOR N. J. A. Sloane, Sep 15 2000 EXTENSIONS a(5) from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 05 2008 a(6)=1091401 is a probable prime discovered by Paul Bourdelais, Mar 10 2014 STATUS approved

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