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A096774
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Numbers k such that 9*10^k + 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, Aug 18 2004
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LINKS
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FORMULA
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EXAMPLE
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k = 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}] (* Robert G. Wilson v, Jan 19 2005 *)
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PROG
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(PARI) for(n=1, 1e5, if(isprime(9*10^n + 7), print1(n", "))) \\ Altug Alkan, Oct 16 2015
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CROSSREFS
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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 Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
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STATUS
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approved
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