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A102930
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Numbers n such that 10^n + 2*R_n + 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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2
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1, 2, 4, 14, 25, 32, 56, 62, 811, 812, 1084, 2533, 11924, 49552
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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 (11*10^n+43)/9 is prime.
a(15) > 10^5. - Robert Price, Jan 16 2015
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LINKS
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Table of n, a(n) for n=1..14.
Makoto Kamada, Prime numbers of the form 122...227.
Index entries for primes involving repunits.
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FORMULA
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a(n) = A102010(n) + 1.
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MATHEMATICA
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Do[ If[ PrimeQ[(11*10^n + 43)/9], Print[n]], {n, 0, 10000}]
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CROSSREFS
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Cf. A002275, A102010.
Sequence in context: A090889 A096012 A261562 * A135113 A050564 A047830
Adjacent sequences: A102927 A102928 A102929 * A102931 A102932 A102933
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KEYWORD
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more,nonn
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AUTHOR
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Robert G. Wilson v, Dec 16 2004
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EXTENSIONS
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Addition of a(13) from Kamada data by Robert Price, Dec 12 2010
a(14) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013
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STATUS
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approved
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