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A152189
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a(n)=Product[(1 + 4*Cos[k*Pi/n]^2)*(1 + 4*Sin[k*Pi/n]^2), {k, 1, Floor[(n - 1)/2]}].
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0
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1, 8, 9, 55, 64, 377, 441, 2583, 3025, 17711, 20735, 121392, 142128, 832040, 974169, 5702887, 6677055, 39088169, 45765225, 267914296, 313679521, 1836311903, 2149991424, 12586269025, 14736260449, 86267571272, 101003831721
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| It appears that Limit[Sqrt[a[n+2]/a[n]],n->Infinity]=1+(Sqrt[5]+1)/2.
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MATHEMATICA
| f[n_] = Product[(1 + 4*Cos[k*Pi/n]^2)*(1 + 4*Sin[k*Pi/n]^2), {k, 1, Floor[(n - 1)/2]}]; Table[N[f[n]], {n, 0, 30}]; Floor[%]
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CROSSREFS
| Sequence in context: A175931 A042847 A121330 * A042873 A033045 A025633
Adjacent sequences: A152186 A152187 A152188 * A152190 A152191 A152192
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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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