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A259141
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Numbers k such that R_k + 9*10^k + 8 is prime, where R_k = 11...11 is the repunit (A002275) of length k.
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0
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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 (82*10^k + 71)/9 is prime.
Terms from Kamada data.
Note Kamada does not recognize k=0 as 17 is a degenerate case of form ABB..BBA.
a(7) > 10^5.
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LINKS
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EXAMPLE
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For k=2, R_2 + 9*10^k + 8 = 11 + 900 + 8 = 919 which is prime.
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MATHEMATICA
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Select[Range[0, 100000], PrimeQ[(82*10^#+71)/9] &]
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CROSSREFS
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KEYWORD
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more,hard,nonn
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AUTHOR
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STATUS
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approved
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