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A103084
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Numbers n such that 8*10^n + 5*R_n - 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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1
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1, 2, 7, 44, 56, 338, 1211, 2693, 3536, 3917, 3974, 4046, 6961, 23771, 69656
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OFFSET
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1,2
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COMMENTS
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Also numbers n such that (77*10^n-23)/9 is prime.
a(16) > 10^5. - Robert Price, Oct 22 2015
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LINKS
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Table of n, a(n) for n=1..15.
Makoto Kamada, Prime numbers of the form 855...553.
Index entries for primes involving repunits.
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FORMULA
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a(n) = A101071(n) + 1.
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MATHEMATICA
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Do[ If[ PrimeQ[(77*10^n - 23)/9], Print[n]], {n, 0, 10000}]
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PROG
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(PARI) for(n=0, 1e5, if(isprime((77*10^n-23)/9), print1(n, ", "))) \\ Altug Alkan, Oct 22 2015
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CROSSREFS
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Cf. A002275, A101071.
Sequence in context: A212270 A270348 A270580 * A041507 A158107 A145073
Adjacent sequences: A103081 A103082 A103083 * A103085 A103086 A103087
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KEYWORD
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more,nonn
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AUTHOR
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Robert G. Wilson v, Jan 19 2005
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EXTENSIONS
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a(14) from Kamada data by Robert Price, Dec 14 2010
a(15) from Robert Price, Oct 22 2015
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STATUS
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approved
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