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A095714
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Numbers n such that 90*R_n + 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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12
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3, 5, 7, 33, 45, 105, 197, 199, 281, 301, 317, 1107, 1657, 3395, 35925, 37597, 64305, 80139, 221631
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Also numbers n such that 10^n - 9 is a prime.
No more terms below 4300. Robert G. Wilson v Oct 15 2004.
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LINKS
| Index entries for primes involving repunits
Makoto Kamada, Factorizations of 99...991
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EXAMPLE
| a(2) = 5, since 10^5 - 9 = 99991, which is prime.
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MATHEMATICA
| Do[ If[ PrimeQ[10^n - 9], Print[n]], {n, 0, 7000}]
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CROSSREFS
| Cf. A088275.
Sequence in context: A162714 A002396 A029508 * A137864 A069969 A067232
Adjacent sequences: A095711 A095712 A095713 * A095715 A095716 A095717
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KEYWORD
| nonn
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AUTHOR
| Alonso Delarte (alonso.delarte(AT)gmail.com), Jul 07 2004
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EXTENSIONS
| More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Oct 15 2004
2 more terms from Jason Earls (zevi_35711(AT)yahoo.com), Jan 07 2008
a(17) - a(19) from Alexander Gramolin, May 13 2011
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