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A102968
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Numbers n such that 3*10^n + 2*R_n + 7 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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1
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3, 5, 9, 12, 27, 51, 53, 147, 155, 257, 519, 603, 2885, 9509, 10524, 19650, 32508, 79445, 158909
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OFFSET
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1,1
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COMMENTS
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Also numbers n such that (29*10^n+61)/9 is prime.
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LINKS
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FORMULA
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MATHEMATICA
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Do[ If[ PrimeQ[(29*10^n + 61)/9], Print[n]], {n, 0, 10000}]
Select[Range[10000], PrimeQ[(29 10^# + 61) / 9] &] (* Vincenzo Librandi, Apr 06 2015 *)
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PROG
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(Magma) [n: n in [0..500] | IsPrime((29*10^n + 61) div 9)]; // Vincenzo Librandi, Apr 06 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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A(13) from Julien Peter Benney (jpbenney(AT)ftml.net), Jan 16 2005
Addition of a(15)-a(16) from Kamada data by Robert Price, Dec 12 2010
a(17) 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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