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A103028
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Numbers n such that 6*10^n + R_n + 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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1
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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 (55*10^n+53)/9 is prime.
a(11) > 10^5. - Robert Price, Sep 07 2015
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LINKS
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Table of n, a(n) for n=1..10.
Makoto Kamada, Prime numbers of the form 611...117.
Index entries for primes involving repunits.
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FORMULA
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a(n) = A101520(n) + 1.
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MATHEMATICA
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Do[ If[ PrimeQ[(55*10^n + 53)/9], Print[n]], {n, 0, 10000}]
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CROSSREFS
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Cf. A002275, A101520.
Sequence in context: A306950 A193419 A160557 * A139732 A037313 A122127
Adjacent sequences: A103025 A103026 A103027 * A103029 A103030 A103031
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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 18 2005
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EXTENSIONS
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a(10) 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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