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A057180
Numbers n such that (14^n + 1)/15 is a prime.
16
7, 53, 503, 1229, 22637, 1091401, 1385203
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 0.82247. The Generalized Repunit Conjecture (see link below) states that this will eventually improve and converge to Euler's Constant (~0.55). - Paul Bourdelais, Mar 10 2014 [updated Paul Bourdelais, Feb 08 2022]
LINKS
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.
PROG
(Prime95) PRP=1, 14, 1091401, 1, 0, 0, "15"
CROSSREFS
Sequence in context: A142981 A350252 A120272 * A137612 A092802 A062207
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
a(7) from Paul Bourdelais, Feb 08 2022
STATUS
approved