A006032 Numbers k such that (14^k - 1)/13 is prime. (Formerly M2670)

3, 7, 19, 31, 41, 2687, 19697, 59693, 67421, 441697

Offset

1,1

References

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

Table of n, a(n) for n=1..10.

Paul Bourdelais, A Generalized Repunit Conjecture

H. Dubner, Generalized repunit primes, Math. Comp., 61 (1993), 927-930.

H. Dubner, Generalized repunit primes, Math. Comp., 61 (1993), 927-930. [Annotated scanned copy]

H. Lifchitz, Mersenne and Fermat primes field

Mathematica

lst={}; Do[If[PrimeQ[(14^n-1)/13], Print[n]; AppendTo[lst, n]], {n, 10^5}]; lst (* Vladimir Joseph Stephan Orlovsky, Aug 21 2008 *)

Prog

(PARI) is(n)=isprime((14^n - 1)/13) \\ Charles R Greathouse IV, Apr 29 2015

Crossrefs

Sequence in context: A360228 A358238 A136054 * A240072 A066148 A093932

Adjacent sequences: A006029 A006030 A006031 * A006033 A006034 A006035

Keyword

hard,nonn,more

Author

N. J. A. Sloane

Extensions

One more term from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 05 2008

a(8) and a(9) correspond to probable primes discovered by Paul Bourdelais, Mar 01 2010

a(10) corresponds to a probable prime discovered by Paul Bourdelais, Dec 08 2014

Status

approved