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A093404
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Primes of the form 70*R_n + 9, where R_n is the repunit (A002275) of length n.
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3
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79, 777777777777777777777777777777777777777777777777777777777777777779, 77777777777777777777777777777777777777777777777777777777777777777777777777777777777779, 777777777777777777777777777777777777777777777777777777777777777777777777777777777777777779
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OFFSET
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1,1
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COMMENTS
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Primes of the form (7*10^n + 11)/9. - Vincenzo Librandi, Nov 16 2010
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LINKS
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Table of n, a(n) for n=1..4.
Makoto Kamada, Prime numbers of the form 77...779.
Index entries for primes involving repunits
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MATHEMATICA
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Select[Table[FromDigits[PadLeft[{9}, n, 7]], {n, 100}], PrimeQ] (* Harvey P. Dale, May 09 2012 *)
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CROSSREFS
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Cf. A002275, A056693 (corresponding n), A098089.
Sequence in context: A060711 A128472 A243432 * A236236 A031136 A050456
Adjacent sequences: A093401 A093402 A093403 * A093405 A093406 A093407
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KEYWORD
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nonn
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AUTHOR
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Rick L. Shepherd, Mar 28 2004
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STATUS
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approved
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