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A102996
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Numbers n such that 4*10^n + 7*R_n + 2 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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1,1
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COMMENTS
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Also numbers n such that (43*10^n+11)/9 is prime.
a(10) > 10^5. - Robert Price, Jun 01 2015
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LINKS
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Table of n, a(n) for n=1..9.
Makoto Kamada, Prime numbers of the form 477...779.
Index entries for primes involving repunits.
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FORMULA
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a(n) = A101733(n) + 1.
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MATHEMATICA
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Do[ If[ PrimeQ[(43*10^n + 11)/9], Print[n]], {n, 0, 10000}]
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CROSSREFS
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Cf. A002275, A101733.
Sequence in context: A218077 A240040 A088888 * A189896 A095182 A104465
Adjacent sequences: A102993 A102994 A102995 * A102997 A102998 A102999
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KEYWORD
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more,nonn
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AUTHOR
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Robert G. Wilson v, Jan 17 2005
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EXTENSIONS
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a(8) from Erik Branger, May 01 2013, submitted by Ray Chandler, Aug 16 2013
a(9) from Robert Price, Jun 01 2015
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STATUS
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approved
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