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Search: id:A046866
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| A046866 |
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Numbers n such that 6*7^n -1 is prime. |
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+0
10
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| 1, 2, 7, 18, 55, 69, 87, 119, 141, 189, 249, 354, 1586, 2135, 2865, 2930, 4214, 7167, 67485, 74402, 79326
(list; graph; listen)
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OFFSET
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1,2
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REFERENCES
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R. K. Guy, Unsolved Problems in Number Theory, Section A3.
H. C. Williams, The primality of certain integers of the form 2Ar^n - 1, Acta Arith. 39 (1981), 7-17.
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MATHEMATICA
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Do[ If[ PrimeQ[6*7^n - 1], Print[n]], {n, 1, 5650}]
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PROGRAM
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(PARI) for(n=1, 2000, if(isprime(6*7^n-1), print(n)))
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CROSSREFS
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Cf. A003307, A002235, A046865, A079906, A001771, A005541, A056725, A046867, A079907.
Sequence in context: A006869 A099626 A046672 this_sequence A000988 A002214 A100408
Adjacent sequences: A046863 A046864 A046865 this_sequence A046867 A046868 A046869
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KEYWORD
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nonn,hard,more
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
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One more term from Jason Earls (zevi_35711(AT)yahoo.com), Jul 21 2001
More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 17 2003
One more term from Ryan Propper (rpropper(AT)stanford.edu), Jun 05 2006
a(19)-a(21) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Nov 26 2008
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