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Search: id:A056719
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| A056719 |
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Numbers n such that 7*10^n + R_n is prime, where R_n = 11...1 is the repunit (A002275) of length n. |
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+0
2
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OFFSET
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1,3
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COMMENT
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Also numbers n such that (64*10^n-1)/9 is prime.
No other terms below 184000 [From Serge Batalov (batalovs(AT)yahoo.com), Aug 13 2009]
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LINKS
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Makoto Kamada, Factorizations of 711...11
Index entries for primes involving repunits
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MATHEMATICA
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Do[ If[ PrimeQ[ 7*10^n + (10^n-1)/9], Print[n]], {n, 0, 35076}]
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CROSSREFS
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Sequence in context: A055056 A009521 A116120 this_sequence A038855 A097254 A043911
Adjacent sequences: A056716 A056717 A056718 this_sequence A056720 A056721 A056722
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KEYWORD
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hard,nonn
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AUTHOR
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Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 11 2000
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EXTENSIONS
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A new PRP term from Serge Batalov (batalovs(AT)yahoo.com), Aug 13 2009
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