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A055559
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Primes of the form 2999...999.
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0
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2, 29, 2999, 2999999, 29999999, 29999999999999999999, 2999999999999999999999999999, 29999999999999999999999999999999999999999999, 29999999999999999999999999999999999999999999999999999999
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OFFSET
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1,1
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COMMENTS
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a(9)=29999999999999999999999999999999999999999999999999999999. - Vincenzo Librandi, Aug 07 2010
The next term (a(10)) has 208 digits, and a(11) has 1312 digits. - Harvey P. Dale, Jan 22 2023
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LINKS
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EXAMPLE
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3*10^k - 1 is prime for {1,3,6,7,19,27,43,55,207}; k gives the number of 9's in these numbers.
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MATHEMATICA
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Select[Table[FromDigits[PadRight[{2}, n, 9]], {n, 60}], PrimeQ] (* Harvey P. Dale, Jan 22 2023 *)
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CROSSREFS
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KEYWORD
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base,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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