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A145106
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Numbers n such that 6^n+5 is prime.
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3
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1, 2, 4, 7, 10, 14, 18, 32, 55, 102, 177, 190, 247, 276, 372, 1524, 1545, 2502, 4966, 5294, 13030, 13785, 14329, 27333, 44224, 93812, 127176, 128640, 136434, 184614, 269407, 311257, 349903, 389756
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OFFSET
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1,2
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COMMENTS
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a(27) > 10^5. - Robert Price, Aug 06 2017
As reported by Lelio R Paula in November 2014 at primenumbers.net/prptop, the following three terms are also in this sequence: 127176, 128640, 136434. It is not confirmed that they are the next terms, however. - Robert Price, Aug 06 2017
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LINKS
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Table of n, a(n) for n=1..34.
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EXAMPLE
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6^1+5=11 and 6^2+5=41, which are both prime, so 1 and 2 are in the sequence. 6^3+5=221 is not prime since it is divisible by 7, so 3 is not in the sequence.
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MATHEMATICA
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Select[Range[0, 100000], PrimeQ[6^# + 5] &] (* Robert Price, Aug 06 2017 *)
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PROG
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(PARI) is(n)=ispseudoprime(6^n+5) \\ Charles R Greathouse IV, Jun 13 2017
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CROSSREFS
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Cf. A059614.
Sequence in context: A183136 A144873 A120679 * A127723 A076268 A323623
Adjacent sequences: A145103 A145104 A145105 * A145107 A145108 A145109
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KEYWORD
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nonn
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AUTHOR
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Dmitry Kamenetsky, Oct 02 2008
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EXTENSIONS
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a(21)-a(26) from Robert Price, Aug 06 2017
a(27)-a(30) from Paul Bourdelais, Jan 28 2021
a(31)-a(34) from Paul Bourdelais, Feb 11 2021
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STATUS
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approved
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