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A097402
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Numbers n such that 6*10^n + 2*R_n + 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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1
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OFFSET
| 1,2
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COMMENTS
| Also numbers n such that (56*10^n+43)/9 is prime.
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LINKS
| Makoto Kamada, Factorizations of 622...227.
Index entries for primes involving repunits.
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EXAMPLE
| 1, 13 are members since 67 and 62222222222227 are primes.
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MATHEMATICA
| Do[ If[ PrimeQ[(56*10^n + 43)/9], Print[n]], {n, 0, 10000}]
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CROSSREFS
| Sequence in context: A139911 A097460 A138353 * A201788 A139873 A142787
Adjacent sequences: A097399 A097400 A097401 * A097403 A097404 A097405
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KEYWORD
| bref,more,nonn
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AUTHOR
| Julien Peter Benney (jpbenney(AT)ftml.net), Nov 11 2004
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