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A088275
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Numbers k such that 10^k + 9 is prime.
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26
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1, 2, 3, 4, 9, 18, 22, 45, 49, 56, 69, 146, 202, 272, 2730, 2841, 4562, 31810, 43186, 48109, 92691, 237670
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OFFSET
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1,2
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COMMENTS
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No others less than 9000. - Julien Peter Benney (jpbenney(AT)ftml.net), Jan 15 2005
No others less than 39254. - Dirk Augustin, Oct 24 2006
2730, 2841 and 4562 all give primes. - Joao da Silva (zxawyh66(AT)yahoo.com), Sep 30 2005
Verified existing terms. No other terms less than 40001. - Robert Price, Aug 14 2010
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LINKS
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FORMULA
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EXAMPLE
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4 is a member since 10^4 + 9 = 10009 is a prime.
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MATHEMATICA
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Do[ If[ PrimeQ[ 10^n + 9], Print[n]], {n, 0, 10000}] (* Robert G. Wilson v, Dec 16 2004 *)
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PROG
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CROSSREFS
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KEYWORD
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nonn,hard,more
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AUTHOR
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EXTENSIONS
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a(17) from Julien Peter Benney (jpbenney(AT)ftml.net), Jan 15 2005
a(18) (a PRP) found by Dirk Augustin, Oct 16 2006
a(19)-a(20) (probable primes), found with WinPFGW. No others less than 60400. - Jason Earls, Dec 22 2007
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STATUS
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approved
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