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A138067
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Least k>1 such that (2n-1)^k + 2 is prime, or 0 if no such number exists.
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1
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2, 2, 3, 0, 2, 5, 0, 2, 105, 0, 2, 11, 0, 5, 3, 0, 2, 15, 0, 2, 9, 0, 2, 113, 0, 5, 7, 0, 2, 27, 0, 3, 3, 0, 3, 3, 0, 12, 61, 0, 2, 3, 0, 4, 255, 0, 8, 63, 0, 2, 9, 0, 2, 3473, 0, 2, 3, 0, 2, 15, 0, 2, 87, 0, 3, 23, 0, 36, 1861, 0, 4, 3, 0, 2, 5, 0, 3, 7, 0, 136, 425, 0, 11
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| a(3n+1) = 0 for n>0.
a(84) > 100000. [From Ray Chandler (rayjchandler(AT)sbcglobal.net), Aug 10 2011]
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CROSSREFS
| Cf. A084713 = Smallest prime of the form (2n-1)^k + 2, or 0 if no such number exists. Cf. A138066 = Least k>0 such that (2n-1)^k + 2 is prime, or 0 if no such number exists. Cf. A051783 = Numbers n such that 3^n + 2 is prime. Cf. A087885 = Numbers n such that 5^n + 2 is prime. Cf. A090649, A109076, A113480, A138048, A138049, A138050, A138051, A087886, A113481.
Sequence in context: A182631 A091426 A053761 * A125093 A103516 A129234
Adjacent sequences: A138064 A138065 A138066 * A138068 A138069 A138070
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KEYWORD
| hard,more,nonn
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AUTHOR
| Alexander Adamchuk (alex(AT)kolmogorov.com), Mar 02 2008
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EXTENSIONS
| a(54)-a(83) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Oct 29 2008
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