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A102997
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Numbers n such that 4*10^n + 8*R_n - 7 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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1
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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 (44*10^n-71)/9 is prime.
No other terms below 10^5.
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LINKS
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FORMULA
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MATHEMATICA
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Do[ If[ PrimeQ[(44*10^n - 71)/9], Print[n]], {n, 10000}]
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PROG
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(PARI) for(n=0, 1000, if(isprime((44*10^n-71)/9), print1(n", "))) \\ Altug Alkan, Oct 15 2015
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CROSSREFS
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KEYWORD
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bref,more,nonn
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AUTHOR
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STATUS
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approved
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