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A103063
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Numbers n such that 7*10^n + 6*R_n - 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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1
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0, 1, 2, 6, 25, 69, 253, 300, 384, 434, 721, 822, 883, 2192, 2649, 3441, 3445, 8028, 11655
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OFFSET
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1,3
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COMMENTS
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Also numbers n such that (23*10^n-17)/3 is prime.
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LINKS
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FORMULA
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EXAMPLE
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For n=0, (23*10^n - 17)/3 = , which is prime.
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MATHEMATICA
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Do[ If[ PrimeQ[(23*10^n - 17)/3], 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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