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 A181876 Denominators of coefficient array of minimal polynomials of cos(2*Pi/n). Rising powers in x. 11
 1, 1, 1, 1, 2, 1, 1, 1, 4, 2, 1, 2, 1, 8, 2, 2, 1, 2, 1, 1, 8, 4, 1, 1, 4, 2, 1, 32, 16, 8, 1, 2, 1, 4, 1, 1, 64, 32, 8, 2, 4, 2, 1, 8, 2, 2, 1, 16, 2, 1, 2, 1, 8, 1, 1, 1, 1, 256, 32, 32, 16, 16, 4, 4, 2, 1, 8, 4, 1, 1, 512, 256, 64, 16, 32, 16, 8, 1, 2, 1, 16, 1, 4, 1, 1, 64, 4, 2, 4, 2, 2 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,5 COMMENTS The corresponding numerator array is A181875(n,m). The sequence of row lengths is d(n)+1, with d(n):=A023022(n), n >= 2, and d(1):=1: [2, 2, 2, 2, 3, 2, 4, 3, 4, 3, 6, 3, 7, 4, 5, 5, 9, 4, 10, 5, 7, ...]. For details on the monic, minimal degree rational polynomial with one of its zeros cos(2*Pi/n), n >= 1 (so-called minimal polynomial of cos(2*Pi/n)), see the array A181875(n,m) where also references are found. REFERENCES See A181875. LINKS See A181875. FORMULA a(n,m) = denominator([x^m]Psi(n,x)), with the minimal polynomial Psi(n,x) of cos(2*Pi/n), n >= 1. See A181875 for details and references. EXAMPLE [1,1], [1,1], [2,1], [1,1], [4,2,1], [2,1], [8,2,2,1], [2,1,1], [8,4,1,1], [4,2,1], ... MATHEMATICA ro[n_] := Denominator[ cc = CoefficientList[ MinimalPolynomial[ Cos[2*Pi/n], x], x] ; cc/Last[cc]]; Flatten[Table[ro[n], {n, 1, 21}]] (* Jean-François Alcover, Sep 27 2011 *) CROSSREFS Cf. A023022, A181875, A181877, A183918. Sequence in context: A235388 A294897 A252733 * A131505 A100092 A131508 Adjacent sequences:  A181873 A181874 A181875 * A181877 A181878 A181879 KEYWORD nonn,easy,tabf AUTHOR Wolfdieter Lang, Jan 08 2011 STATUS approved

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Last modified May 8 13:26 EDT 2021. Contains 343666 sequences. (Running on oeis4.)