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A102975
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Numbers n such that 3*10^n + 6*R_n + 1 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, 12, 15, 51, 194, 498, 2136, 2822, 3762, 7428, 22740, 30452, 37952, 55254
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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+1)/3 is prime.
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LINKS
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FORMULA
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MATHEMATICA
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Do[ If[ PrimeQ[(11*10^n+1)/3], Print[n]], {n, 0, 10000}]
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PROG
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(Magma) [n: n in [0..300] | IsPrime((11*10^n+1) div 3)]; // Vincenzo Librandi, Dec 01 2015
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CROSSREFS
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KEYWORD
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more,nonn
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AUTHOR
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EXTENSIONS
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Addition of a(12) from Kamada data by Robert Price, Dec 13 2010
a(13)-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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