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A057185 Numbers n such that (19^n + 1)/20 is a prime. 15
17, 37, 157, 163, 631, 7351, 26183, 30713, 41201, 77951, 476929 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..11.

P. 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

MATHEMATICA

Select[Range[0, 10000], PrimeQ[((19^# + 1) / 20)] &] (* Vincenzo Librandi, Mar 20 2015 *)

PROG

(PRIME95) PRP=1, 19, 476929, 1, 0, 0, "20" # Paul Bourdelais, Mar 20 2015

CROSSREFS

Sequence in context: A060429 A052292 A154301 * A157467 A093343 A153685

Adjacent sequences:  A057182 A057183 A057184 * A057186 A057187 A057188

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Sep 15 2000

EXTENSIONS

26183 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 05 2008

a(8)-a(9) give probable primes discovered by Paul Bourdelais, Mar 15 2010

a(10) gives a probable prime discovered by Paul Bourdelais, Mar 18 2010

a(11) gives a probable prime discovered by Paul Bourdelais, Mar 20 2015

STATUS

approved

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Last modified December 14 16:38 EST 2019. Contains 329979 sequences. (Running on oeis4.)