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A102986
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Numbers n such that 4*10^n + 2*R_n + 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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1
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1, 4, 136, 181, 325, 3292, 3871, 4690, 7876, 11911, 16096, 21649, 43045
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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 (38*10^n+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[(38*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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Addition of a(10)-a(12) from Kamada data by Robert Price, Dec 13 2010
a(13) 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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