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A146308
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a(n) = such n that numerator of (n-6)/(2n) = n and n=0,1,2,3,...: a(n) = index of first occurence n in A146306.
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3
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6, 7, 14, 15, 22, 11, 78, 13, 38, 33, 46, 17, 150, 19, 62, 51, 70, 23, 222, 25, 86, 69, 94, 29, 294, 31, 110, 87, 118, 35, 366, 37, 134, 105, 142, 41, 438, 43, 158, 123, 166, 47, 510, 49, 182, 141, 190, 53, 582, 55, 206, 159, 214, 59, 654, 61, 230, 177, 238, 65, 726
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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COMMENTS
| General formula (*Artur Jasinski*):
2 Cos[2*Pi/n] = Hypergeometric2F1[(n-6)/(2n),(n+6)/(2n),1/2,3/4] =
Hypergeometric2F1[A146306(n)/A146307(n),A146306(n+12)/A146307(n),1/2,3/4].
2 Cos[2*Pi/n] is root of polynomial of degree = EulerPhi[n]/2 = A000010(n)/2 = A023022(n).
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MATHEMATICA
| aa = {}; Do[k = 1; While[Numerator[(k - 6)/(2 k)] != n, k++ ]; AppendTo[aa, k], {n, 0, 100}]; aa (*Artur Jasinski*)
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CROSSREFS
| A007310, A051724, A146306, A146307, A146309.
Sequence in context: A041319 A042315 A080402 * A047589 A125996 A058556
Adjacent sequences: A146305 A146306 A146307 * A146309 A146310 A146311
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KEYWORD
| nonn
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AUTHOR
| Artur Jasinski (grafix(AT)csl.pl), Oct 29 2008
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