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Search: id:A055034
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| A055034 |
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a(1) = 1, a(n) = phi(2n)/2 for n>1. |
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+0
4
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| 1, 1, 1, 2, 2, 2, 3, 4, 3, 4, 5, 4, 6, 6, 4, 8, 8, 6, 9, 8, 6, 10, 11, 8, 10, 12, 9, 12, 14, 8, 15, 16, 10, 16, 12, 12, 18, 18, 12, 16, 20, 12, 21, 20, 12, 22, 23, 16, 21, 20, 16, 24, 26, 18, 20, 24, 18, 28, 29, 16, 30, 30, 18, 32, 24, 20, 33, 32, 22, 24, 35, 24, 36, 36, 20, 36, 30
(list; graph; listen)
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OFFSET
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1,4
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COMMENT
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Degree of minimal polynomial of cos(pi/n) over the rationals.
For n>1, gives number of times n appears in A094192. - Lekraj Beedassy (blekraj(AT)yahoo.com), Jun 04 2004
Number of integers less than n and having the opposite parity to n that are relatively prime to n. - Anne M. Donovan (anned3005(AT)aol.com), Jul 18 2005
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LINKS
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T. D. Noe, Table of n, a(n) for n=1..2000
Eric Weisstein's World of Mathematics, Trigonometry Angles
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MATHEMATICA
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a[n_] := If[n==1, 1, EulerPhi[n]/{1, 2}[[Mod[n, 2]+1]]];
a[n_] := If[n==1, 1, EulerPhi[2n]/2];
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CROSSREFS
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Cf. A000010.
Sequence in context: A152803 A016729 A060473 this_sequence A112184 A112213 A085755
Adjacent sequences: A055031 A055032 A055033 this_sequence A055035 A055036 A055037
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KEYWORD
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easy,nonn
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AUTHOR
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Shawn Cokus (Cokus(AT)math.washington.edu)
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EXTENSIONS
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Better description from Benoit Cloitre (benoit7848c(AT)orange.fr), Feb 01 2002
Edited by Ray Chandler (rayjchandler(AT)sbcglobal.net), Jul 20 2005
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