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Search: id:A075539
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| A075539 |
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Perfect powers n such that (n-5)/2 is prime. |
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+0
1
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| 9, 27, 2187, 19683, 300763, 1092727, 2048383, 6128487
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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9=3^2, 27=3^3, 2187=3^7, 19683=3^9, but 300763=67^3 - is there any rule?
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MATHEMATICA
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pp = Join[{1}, Select[ Range[10^7], Apply[GCD, Last[ Transpose[ FactorInteger[ # ]]]] > 1 & ]]; Select[pp, PrimeQ[(# - 5)/2] & ]
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CROSSREFS
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Sequence in context: A020254 A124396 A020281 this_sequence A053825 A033479 A034116
Adjacent sequences: A075536 A075537 A075538 this_sequence A075540 A075541 A075542
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KEYWORD
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easy,nonn
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AUTHOR
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Zak Seidov (zakseidov(AT)yahoo.com), Oct 11 2002
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EXTENSIONS
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Extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Oct 14 2002
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