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A103056
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Numbers n such that 7*10^n + 3*R_n + 6 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, 5, 7, 85, 345, 1595, 2105, 6386, 9119, 9332, 14707, 72560
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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 (22*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, (22*10^n+17)/3 = 13 which is a prime so 0 is a term.
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MATHEMATICA
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Do[ If[ PrimeQ[(22*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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