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A089379
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Numbers n such that 10^n + n is prime.
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2
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OFFSET
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1,2
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COMMENTS
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a(8) > 10^5. - Robert Price, Feb 14 2015
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LINKS
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Table of n, a(n) for n=1..7.
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EXAMPLE
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a(2)=9 because 10^9 + 9 is prime.
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MATHEMATICA
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Do[If[Mod[n, 3]!=2&& PrimeQ[10^n+n], Print[n]], {n, 1, 15500, 2}] (* Farideh Firoozbakht, Jun 11 2006 *)
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PROG
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(PARI) is(n)=ispseudoprime(10^n+n) \\ Charles R Greathouse IV, Jun 12 2017
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CROSSREFS
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Cf. A110066.
Sequence in context: A024119 A120306 A197425 * A193698 A188800 A297393
Adjacent sequences: A089376 A089377 A089378 * A089380 A089381 A089382
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KEYWORD
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nonn
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AUTHOR
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Shyam Sunder Gupta, Dec 27 2003
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EXTENSIONS
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One more term from Farideh Firoozbakht, Jun 11 2006
a(7) from Robert Price, Feb 14 2015
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STATUS
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approved
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