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A096774
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Numbers n such that 9*10^n + 7 is prime.
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2
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1, 2, 3, 4, 5, 15, 19, 20, 46, 52, 53, 192, 380, 588, 776, 906, 1350, 1736, 2914, 7508, 15710, 16453, 17488, 18109, 21604, 25891, 26725, 34838, 67468
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OFFSET
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1,2
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COMMENTS
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a(1) through a(12) have been certified prime. a(13) through a(19) are all Fermat and Lucas PRPs. No others less than 6300. - Jason Earls (zevi_35711(AT)yahoo.com), Aug 18 2004
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LINKS
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Table of n, a(n) for n=1..29.
Makoto Kamada, Factorizations of 900...007.
Sabin Tabirca and Kieran Reynolds, Lacunary Prime Numbers.
Index entries for primes involving repunits.
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EXAMPLE
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n = 5; (9*10^5)+7 = 900007, which is prime.
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MATHEMATICA
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Do[ If[ PrimeQ[9*10^n + 7], Print[n]], {n, 0, 10000}] (from Robert G. Wilson v Jan 19 2005)
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CROSSREFS
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Sequence in context: A199165 A202423 A171593 * A201356 A183528 A145029
Adjacent sequences: A096771 A096772 A096773 * A096775 A096776 A096777
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KEYWORD
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more,nonn
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AUTHOR
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Julien Peter Benney (jpbenney(AT)ftml.net), Aug 16 2004
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EXTENSIONS
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More terms from Jason Earls (zevi_35711(AT)yahoo.com), Aug 18 2004
a(20) from Robert G. Wilson v, Jan 19 2005
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
a(25)-a(29) from Kamada data by Robert Price, Dec 14 2010
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STATUS
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approved
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