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A090669
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Numbers n such that 7^n - 2 is a prime.
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15
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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; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| No more terms through 50000. [From Ryan Propper (rpropper(AT)cs.stanford.edu), Dec 07 2008]
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EXAMPLE
| 7^12 -2 = 13841287199 a prime number
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MATHEMATICA
| Do[ If[ PrimeQ[7^n - 2], Print[n]], {n, 1, 2000}] (from Robert G. Wilson v Dec 22 2003)
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CROSSREFS
| Sequence in context: A001839 A087686 A088413 * A079374 A190808 A018614
Adjacent sequences: A090666 A090667 A090668 * A090670 A090671 A090672
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KEYWORD
| nonn
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AUTHOR
| Herman H. Rosenfeld (herm3(AT)pacbell.net), Dec 16 2003
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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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