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A093947
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Primes of the form 8*10^n - 1.
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0
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7, 79, 79999, 799999, 799999999, 79999999999, 79999999999999999999999999, 79999999999999999999999999999999999999999999999999, 79999999999999999999999999999999999999999999999999999999999999999999999999999
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OFFSET
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1,1
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COMMENTS
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Equivalently, primes of the form 7*10^n + 9*R_n, where R_n is the repunit (A002275) of length n.
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LINKS
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MATHEMATICA
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Select[Table[FromDigits[PadRight[{7}, n, 9]], {n, 50}], PrimeQ] (* Vincenzo Librandi, May 08 2019 *)
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PROG
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(Magma) [a: n in [0..200] | IsPrime(a) where a is (8*10^n-1)]; // Vincenzo Librandi, May 08 2019
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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