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A101393
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Numbers k such that 3*10^k + R_k + 6 is prime, where R_k = 11...1 is the repunit (A002275) of length k.
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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 k such that (28*10^k + 53)/9 is prime.
All except 1, 2 and 218 only probably prime. No others less than 10000.
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LINKS
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FORMULA
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EXAMPLE
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n = 1, 2 are members since 37 and 317 are primes.
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MATHEMATICA
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Do[ If[ PrimeQ[(28*10^n+53)/9], Print[n]], {n, 0, 10000}]
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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Julien Peter Benney (jpbenney(AT)ftml.net), Jan 15 2005
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EXTENSIONS
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STATUS
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approved
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