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A102948
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Numbers k such that 2*10^k + R_k + 2 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
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1
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1, 3, 7, 13, 24, 30, 48, 52, 163, 175, 219, 228, 261, 754, 951, 1344, 1573, 3294, 3523, 14161, 70794
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OFFSET
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1,2
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COMMENTS
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Also numbers k such that (19*10^k + 17)/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[(19*10^n + 17)/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(20) from Kamada data by Robert Price, Dec 09 2010
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STATUS
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approved
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