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A103001
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Numbers n such that 5*10^n - 9 is prime.
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2
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1, 2, 4, 7, 24, 172, 173, 218, 439, 2563, 2782, 2880, 3715, 4392, 10820, 14592, 25054, 27769, 40168
(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 - 8 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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LINKS
| Makoto Kamada, Factorizations of 499...991.
Index entries for primes involving repunits.
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MATHEMATICA
| Do[ If[ PrimeQ[5*10^n - 9], Print[n]], {n, 0, 10000}]
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CROSSREFS
| Sequence in context: A138049 A099387 A036440 * A179386 A065846 A047904
Adjacent sequences: A102998 A102999 A103000 * A103002 A103003 A103004
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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
| More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
Addition of a(17)-a(19) from Kamada data by Robert Price (pamandbobprice(AT)yahoo.com), Dec 10 2010
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