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Search: id:A143207
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| A143207 |
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Numbers with exactly 3 distinct prime factors not greater than 5. |
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+0
15
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| 30, 60, 90, 120, 150, 180, 240, 270, 300, 360, 450, 480, 540, 600, 720, 750, 810, 900, 960, 1080, 1200, 1350, 1440, 1500, 1620, 1800, 1920, 2160, 2250, 2400, 2430, 2700, 2880, 3000, 3240, 3600, 3750, 3840, 4050, 4320, 4500, 4800, 4860
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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A001221(a(n))=3; A020639(a(n))=2; A006530(a(n))=5;
A143201(a(n)) = 6;
subsequence of A143204 and of A051037.
Successive k such that EulerPhi[x]/x=4/15. [From Artur Jasinski (grafix(AT)csl.pl), Nov 07 2008]
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LINKS
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T. D. Noe, Table of n, a(n) for n=1..1000
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MATHEMATICA
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a = {}; Do[If[EulerPhi[x]/x == 4/15, AppendTo[a, x]], {x, 1, 11664}]; a [From Artur Jasinski (grafix(AT)csl.pl), Nov 07 2008]
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CROSSREFS
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Cf. A069819.
Sequence in context: A056954 A050519 A069819 this_sequence A108454 A064783 A053014
Adjacent sequences: A143204 A143205 A143206 this_sequence A143208 A143209 A143210
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KEYWORD
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nonn
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AUTHOR
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Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Aug 12 2008
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