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A102929
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Numbers k such that 10^k + 2*R_k + 1 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
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1
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0, 1, 3, 9, 48, 58, 153, 261, 876, 1179, 1596, 17715, 63718
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OFFSET
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1,3
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COMMENTS
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Also numbers k such that (11*10^k + 7)/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[(11*10^n + 7)/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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Addition of a(12) from Kamada data by Robert Price, Dec 13 2010
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STATUS
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approved
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