1,1

Prime repunits in base 6.

J. Brillhart et al., Factorizations of b^n +- 1. Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 2nd edition, 1985; and later supplements.

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

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

S. S. Wagstaff, Jr., The Cunningham Project

Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.

J. Brillhart et al., Factorizations of b^n +- 1, Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 3rd edition, 2002.

H. Lifchitz, Mersenne and Fermat primes field

lst={}; Do[If[PrimeQ[(6^n-1)/5], Print[n]; AppendTo[lst, n]], {n, 10^5}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Aug 21 2008]

Sequence in context: A061092 A084435 A072469 this_sequence A037151 A008840 A156313

Adjacent sequences: A004059 A004060 A004061 this_sequence A004063 A004064 A004065

hard,nonn

N. J. A. Sloane (njas(AT)research.att.com).

More terms from Kamil Duszenko (kdusz(AT)wp.pl), Jun 22 2003

a(14)=79987, discovered Nov 05 2007, is a probable prime based on trial factoring to 1E11 and Fermat primality test base 2. - Paul Bourdelais (paul.bourdelais(AT)gd-ais.com).