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A102993
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Numbers n such that 4*10^n + 5*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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6, 21, 22, 24, 51, 81, 132, 165, 621, 1450, 3424, 5979, 11526, 26980, 49233, 84927
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OFFSET
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1,1
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COMMENTS
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Also numbers n such that (41*10^n+31)/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[(41*10^n + 31)/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(13)-a(14) from Kamada data by Robert Price, Dec 12 2010
a(15) 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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