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A102940
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Numbers n such that 10^n + 6*R_n + 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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1
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0, 1, 2, 3, 5, 9, 11, 14, 32, 54, 55, 60, 153, 200, 461, 569, 840, 847, 1296, 1356, 2007, 2627, 2847, 3110, 6876, 9161, 17765
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| Also numbers n such that (5*10^n+1)/3 is prime.
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LINKS
| Makoto Kamada, Factorizations of 166...667.
Index entries for primes involving repunits.
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MATHEMATICA
| Do[ If[ PrimeQ[(5*10^n + 1)/3], Print[n]], {n, 0, 10000}]
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CROSSREFS
| Numbers n such that A126109(n) is prime.
Cf. A000040, A126109.
Sequence in context: A137518 A137509 A014109 * A157049 A195668 A059042
Adjacent sequences: A102937 A102938 A102939 * A102941 A102942 A102943
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KEYWORD
| more,nonn
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AUTHOR
| Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 16 2004
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EXTENSIONS
| Edited by N. J. A. Sloane (njas(AT)research.att.com), Mar 16 2007
Addition of a(27) from Kamada data by Robert Price (pamandbobprice(AT)yahoo.com), Dec 08 2010
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