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A090669 Numbers n such that 7^n - 2 is a prime. +0
16
1, 2, 4, 7, 8, 12, 15, 28, 31, 84, 98, 128, 238, 302, 859, 1508, 1586, 2091, 2796, 2888, 3924, 4815, 5636, 6596, 7090, 20176, 22176 (list; graph; listen)
OFFSET

1,2

COMMENT

No more terms through 50000. [From Ryan Propper (rpropper(AT)cs.stanford.edu), Dec 07 2008]

EXAMPLE

7^12 -2 = 13841287199 a prime number

MATHEMATICA

Do[ If[ PrimeQ[7^n - 2], Print[n]], {n, 1, 2000}] (from Robert G. Wilson v Dec 22 2003)

CROSSREFS

Sequence in context: A001839 A087686 A088413 this_sequence A079374 A018614 A004616

Adjacent sequences: A090666 A090667 A090668 this_sequence A090670 A090671 A090672

KEYWORD

nonn

AUTHOR

Herman H. Rosenfeld (herm3(AT)pacbell.net), Dec 16 2003

EXTENSIONS

Corrected and extended by Robert G. Wilson v (rgwv(AT)rgwv.com) and Ray Chandler (rayjchandler(AT)sbcglobal.net), Dec 22 2003)

Three more terms. Ryan Propper (rpropper(AT)cs.stanford.edu), Dec 07 2008

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Last modified December 20 00:58 EST 2009. Contains 171054 sequences.


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