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Search: id:A101392
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| A101392 |
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Numbers n such that 2*10^n+9 is prime. |
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+0
2
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OFFSET
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1,2
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COMMENT
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761 and 9205 only probably prime. No others less than 10000.
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LINKS
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Makoto Kamada, Factorizations of 200...009.
Sabin Tabiraca and Kieran Reynolds, Lacunary Prime Numbers.
Index entries for primes involving repunits.
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EXAMPLE
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n = 1, 5 are members since 29 and 200009 are primes.
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MATHEMATICA
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Do[ If[ PrimeQ[2*10^n + 9], Print[n]], {n, 0, 10000}]
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CROSSREFS
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Cf. A081677, A088275.
Sequence in context: A145773 A072324 A082026 this_sequence A078260 A007185 A030995
Adjacent sequences: A101389 A101390 A101391 this_sequence A101393 A101394 A101395
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KEYWORD
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hard,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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More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
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