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A102945
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Numbers k such that 10^k + 8*R_k + 1 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
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3
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OFFSET
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1,2
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COMMENTS
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Also numbers k such that (17*10^k + 1)/9 is prime.
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LINKS
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FORMULA
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MAPLE
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MATHEMATICA
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Do[ If[ PrimeQ[(17*10^n + 1)/9], Print[n]], {n, 0, 10000}]
Select[Range[1000], PrimeQ[(17 10^# + 1) / 9] &] (* Vincenzo Librandi, Nov 17 2014 *)
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PROG
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(Magma) [n: n in [0..300] | IsPrime((17*10^n+1) div 9)]; // Vincenzo Librandi, Nov 17 2014
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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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More PRP terms a(7)-a(10). Sieved with srsieve and tested with Prime95 by Serge Batalov, May 15 2010
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STATUS
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approved
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