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A103048
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Numbers n such that 7*10^n-9 is prime.
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1
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1, 2, 3, 4, 14, 15, 23, 28, 54, 100, 272, 373, 403, 568, 639, 842, 969, 1255, 1259, 3047, 4838, 6389, 12755, 15142, 34943, 37652, 38108, 38686, 39384, 43393, 47280, 55030
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Also numbers n such that 6*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 699...991.
Index entries for primes involving repunits.
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MATHEMATICA
| Do[ If[ PrimeQ[7*10^n - 9], Print[n]], {n, 0, 10000}]
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CROSSREFS
| Sequence in context: A171573 A039576 A091907 * A140128 A167906 A100998
Adjacent sequences: A103045 A103046 A103047 * A103049 A103050 A103051
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KEYWORD
| more,nonn
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AUTHOR
| Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 18 2005
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EXTENSIONS
| More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
Addition of a(25)-a(32) from Kamada data by Robert Price (pamandbobprice(AT)yahoo.com), Dec 13 2010
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