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A103002
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Numbers n such that 5*10^n - 7 is prime.
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2
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1, 3, 4, 8, 14, 16, 24, 61, 80, 87, 104, 108, 144, 2157, 3325, 4122, 20718, 51163
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Also numbers n such that 4*10^n + 9*R_n - 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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LINKS
| Makoto Kamada, Factorizations of 499...993.
Index entries for primes involving repunits.
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MATHEMATICA
| Do[ If[ PrimeQ[5*10^n - 7], Print[n]], {n, 0, 10000}]
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CROSSREFS
| Sequence in context: A121980 A091231 A049893 * A181408 A004979 A051788
Adjacent sequences: A102999 A103000 A103001 * A103003 A103004 A103005
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KEYWORD
| more,nonn
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AUTHOR
| Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 17 2005
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EXTENSIONS
| Addition of a(17)-a(18) from Kamada data by Robert Price (pamandbobprice(AT)yahoo.com), Dec 10 2010
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