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A152192
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A product sequence of Fibonacci type: a(n)=Product[(1 + 4*Cos[2*Pi*k/n]^2), {k, 1, Floor[(n - 1)/2]}.
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0
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1, 1, 1, 2, 1, 5, 4, 13, 9, 34, 25, 89, 64, 233, 169, 610, 441, 1597, 1156, 4181, 3025, 10946, 7921, 28657, 20736, 75025, 54289, 196418, 142129, 514229, 372100
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,4
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COMMENTS
| Sqrt[a[n+2]/a[n]]=(Sqrt[5]+1)/2.
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FORMULA
| G.f.:(1+x^6-x^5-3*x^4-x^2+x)/((x^2+1)*(x^2+x-1)*(x^2-x-1)) [From Maksym Voznyy (voznyy(AT)mail.ru), Jul 26 2009]
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MATHEMATICA
| Clear[f, n, k]; f[n_] := Product[(1 + 4*Cos[2*Pi*k/n]^2), {k, 1, Floor[(n - 1)/2]}]; a = Table[N[f[n]], {n, 0, 30}]
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CROSSREFS
| Sequence in context: A091802 A144240 A119914 * A120924 A079285 A124660
Adjacent sequences: A152189 A152190 A152191 * A152193 A152194 A152195
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KEYWORD
| nonn
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AUTHOR
| Roger L. Bagula and Gary W. Adamson (rlbagulatftn(AT)yahoo.com), Nov 28 2008
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