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A103010
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Numbers k such that 5*10^k + 2*R_k + 5 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
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1
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3, 5, 33, 48, 59, 60, 74, 126, 177, 228, 638, 1304, 1644, 2435, 4374, 8750, 15114, 16853, 30353, 30545, 36236
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OFFSET
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1,1
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COMMENTS
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Also numbers k such that (47*10^k + 43)/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[(46*10^n + 43)/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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a(19)-a(21) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013
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STATUS
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approved
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