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A103018
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Numbers n such that 5*10^n + 6*R_n + 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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1
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1, 2, 3, 10, 25, 29, 34, 73, 76, 77, 651, 884, 938, 1252, 1893, 3342, 4034, 6168, 6216, 6231, 6812, 11046, 15448, 16628, 16918, 18734, 45935, 130393, 139289, 158819
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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 (17*10^n+7)/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[(17*10^n + 7)/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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a(22)-a(26) from Kamada link by Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
a(27) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013
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STATUS
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approved
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