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A103078
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Numbers n such that 8*10^n + 3*R_n + 6 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, 4, 9, 10, 15, 44, 55, 56, 124, 140, 279, 674, 848, 1420, 1462, 3314, 3442, 4141, 35625
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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 (25*10^n+17)/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[(25*10^n + 17)/3], Print[n]], {n, 0, 10000}]
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PROG
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(PARI) for(n=1, 1e3, if(isprime((25*10^n+17)/3), print1(n", "))) \\ Altug Alkan, Oct 20 2015
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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(20) 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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