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A056725
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Numbers n such that 9*10^n - 1 is prime.
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11
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1, 3, 7, 19, 29, 37, 93, 935, 8415, 9631, 11143, 41475, 41917, 48051, 107663
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Also numbers n such that 8*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 899...99
Index entries for primes involving repunits
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MATHEMATICA
| Do[ If[ PrimeQ[ 8*10^n + (10^n-1)], Print[n]], {n, 1, 6750, 2}]
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CROSSREFS
| Cf. A003307, A002235, A046865, A079906, A046866, A001771, A005541, A046867, A079907.
Sequence in context: A171140 A186452 A016046 * A091738 A136054 A006032
Adjacent sequences: A056722 A056723 A056724 * A056726 A056727 A056728
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KEYWORD
| hard,nonn,more
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AUTHOR
| Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 11 2000
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EXTENSIONS
| More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
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