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A102989
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Numbers n such that 4*10^n + 3*R_n + 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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1
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1, 3, 5, 6, 8, 15, 26, 53, 60, 97, 183, 205, 302, 396, 456, 467, 607, 828, 1860, 2743, 4273, 4781, 5712, 6038, 6637, 9222, 10832, 18865, 25848, 42247, 48547, 87565, 95588
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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 (13*10^n+11)/3 is prime.
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LINKS
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FORMULA
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MATHEMATICA
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Do[ If[ PrimeQ[(13*10^n + 11)/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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Addition of a(27)-a(29) from Kamada data by Robert Price, Dec 08 2010
a(30)-a(31) from Erik Branger, May 01 2013, submitted by Ray Chandler, Aug 16 2013
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STATUS
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approved
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