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A057172
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Numbers n such that (6^n + 1)/7 is a prime.
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1
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3, 11, 31, 43, 47, 59, 107, 811, 2819, 4817, 9601, 33581, 38447, 41341, 131891, 196337
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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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.
Eric Weisstein's World of Mathematics, Repunit
H. Lifchitz, Mersenne and Fermat primes field
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MAPLE
| PFGW v3.3.1 [From Paul Bourdelais (pbourdelais(AT)radiantblue.com), Feb 01 2010]
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MATHEMATICA
| lst={}; Do[p=(6^n+1)/7; If[PrimeQ[p], AppendTo[lst, n]], {n, 7!}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Sep 29 2008]
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PROG
| (Other) PFGW v3.3.1 [From Paul Bourdelais (pbourdelais(AT)radiantblue.com), Feb 19 2010]
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CROSSREFS
| Sequence in context: A003523 A018781 A119215 * A071568 A093406 A097081
Adjacent sequences: A057169 A057170 A057171 * A057173 A057174 A057175
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Sep 15 2000
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EXTENSIONS
| a(12) was discovered by Kamil Duszenko, Jul 15 2003; a(13) was discovered by Henri Lifchitz Sep 15 2007; a(14) was discovered by Paul Bourdelais, Oct 01 2007.
a(15)=131891, a probable prime, was discovered by Paul Bourdelais (pbourdelais(AT)radiantblue.com), Feb 01 2010
a(16)=196337 is a probable prime discovered by Paul Bourdelais (pbourdelais(AT)radiantblue.com), Feb 19 2010
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