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A103065
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Numbers n such that 7*10^n + 6*R_n + 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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1
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1, 2, 3, 6, 8, 18, 19, 21, 32, 48, 65, 72, 99, 120, 201, 308, 717, 968, 1344, 2132, 3567, 3968, 8327, 10598, 12465, 15875, 18895, 28611, 29418
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Also numbers n such that (23*10^n+7)/3 is prime.
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LINKS
| Makoto Kamada, Factorizations of 766...669.
Index entries for primes involving repunits.
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MATHEMATICA
| Do[ If[ PrimeQ[(23*10^n + 7)/3], Print[n]], {n, 0, 10000}]
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CROSSREFS
| Sequence in context: A056348 A057574 A198296 * A005508 A110448 A064450
Adjacent sequences: A103062 A103063 A103064 * A103066 A103067 A103068
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KEYWORD
| more,nonn
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AUTHOR
| Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 19 2005
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EXTENSIONS
| More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
a(28)-a(29) from Kamada data by Robert Price (pamandbobprice(AT)yahoo.com), Dec 14 2010
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