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A056703
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Numbers n such that 3*10^n - 1 is prime.
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1
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0, 1, 3, 6, 7, 19, 27, 43, 55, 207, 1311, 3204, 7050, 9439, 26044, 33058, 34507, 49314, 119292
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| Also numbers n such that 2*10^n + 9*R_n is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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LINKS
| Makoto Kamada, Factorizations of 299...99
Index entries for primes involving repunits
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MATHEMATICA
| Do[ If[ PrimeQ[ 2*10^n + (10^n-1)], Print[n]], {n, 0, 3000}]
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CROSSREFS
| Sequence in context: A192124 A072773 A130049 * A103831 A106357 A088101
Adjacent sequences: A056700 A056701 A056702 * A056704 A056705 A056706
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KEYWORD
| hard,nonn,more
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AUTHOR
| Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 10 2000
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EXTENSIONS
| More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
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