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A103089
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Numbers n such that 8*10^n + 7*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, 5, 6, 185, 401, 480, 1319, 5646, 6029, 16824, 62387, 70638
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OFFSET
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1,2
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COMMENTS
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Also numbers n such that (79*10^n-61)/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[(79*10^n - 61)/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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Inserted a(1)=0 and added a(11)-a(12) by Robert Price, Oct 25 2015
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STATUS
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approved
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