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Search: id:A146307
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| A146307 |
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a(n) = denominator of (n-6)/(2n)=denominator of (n+6)/(2n) |
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+0
4
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| 2, 1, 2, 4, 10, 1, 14, 8, 6, 5, 22, 4, 26, 7, 10, 16, 34, 3, 38, 20, 14, 11, 46, 8, 50, 13, 18, 28, 58, 5, 62, 32, 22, 17, 70, 12, 74, 19, 26, 40, 82, 7, 86, 44, 30, 23, 94, 16, 98, 25, 34, 52, 106, 9, 110, 56, 38, 29, 118, 20, 122, 31, 42, 64, 130, 11, 134, 68, 46, 35, 142, 24
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OFFSET
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1,1
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COMMENT
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For numerators see A146306.
General formula (*Artur Jasinski*):
2 Cos[2*Pi/n] = Hypergeometric2F1[(n-6)/(2n),(n+6)/(2n),1/2,3/4] =
Hypergeometric2F1[A146306(n)/a(n),A146306(n+12)/a(n),1/2,3/4].
2 Cos[2*Pi/n] is root of polynomial of degree = EulerPhi[n]/2 = A000010(n)/2 = A023022(n).
Records in this sequence are even and are congruent to 2 or 10 mod 12 (see A091999).
Indices where odd numbers occured in this seuqnce are 4n-2 (see A016825). Indices where prime numbers occured in this sequence see A146309.
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MATHEMATICA
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Table[Denominator[(n - 6)/(2 n)], {n, 1, 100}] (*Artur Jasinski*)
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CROSSREFS
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A007310, A051724, A146306, A146308
Sequence in context: A024959 A029728 A135547 this_sequence A063894 A024500 A000087
Adjacent sequences: A146304 A146305 A146306 this_sequence A146308 A146309 A146310
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KEYWORD
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nonn
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AUTHOR
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Artur Jasinski (grafix(AT)csl.pl), Oct 29 2008
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