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A096846
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Numbers n for which -1+8*R_n - 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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6
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1, 3, 4, 6, 9, 12, 72, 118, 124, 190, 244, 304, 357, 1422, 2691, 5538, 7581
(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-17)/9 is prime.
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LINKS
| Index entries for primes involving repunits
Makoto Kamada, Factorizations of 88...887.
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FORMULA
| Equals A056695 + 1. - Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
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EXAMPLE
| n=72:
888888888888888888888888888888888888888888888888888888888888888888888887 is prime.
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MATHEMATICA
| Do[ If[ PrimeQ[ 8(10^n - 1)/9 + 1], Print[n]], {n, 5000}] (from Robert G. Wilson v Oct 15 2004)
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CROSSREFS
| Cf. A096503, A096504, A096505, A096506, A096507, A096508, A096841, A096842, A096843, A096844, A096845, A096846, A000203.
Sequence in context: A097922 A103109 A078743 * A140570 A032720 A167928
Adjacent sequences: A096843 A096844 A096845 * A096847 A096848 A096849
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KEYWORD
| more,nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), Jul 15 2004
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EXTENSIONS
| More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
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