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A103043
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Numbers n such that 6*10^n + 7*R_n + 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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1
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3, 5, 15, 47, 69, 123, 713, 2316, 6147, 8877, 10704
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OFFSET
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1,1
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COMMENTS
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Also numbers n such that (61*10^n+11)/9 is prime.
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LINKS
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FORMULA
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MATHEMATICA
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Do[ If[ PrimeQ[(61*10^n + 11)/9], Print[n]], {n, 0, 10000}]
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CROSSREFS
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KEYWORD
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more,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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