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A093400
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Primes of the form 10*R_k + 9, where R_k is the repunit (A002275) of length k.
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1
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OFFSET
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1,1
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COMMENTS
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LINKS
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MATHEMATICA
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Select[Table[FromDigits[PadLeft[{9}, n, 1]], {n, 1000}], PrimeQ] (* Harvey P. Dale, Dec 11 2013 *)
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CROSSREFS
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Cf. A056659 (corresponding k and count of digits 1 in a(n)).
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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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