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A131714
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Period 6: repeat [1, -2, 2, -1, 2, -2].
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2
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1, -2, 2, -1, 2, -2, 1, -2, 2, -1, 2, -2, 1, -2, 2, -1, 2, -2, 1, -2, 2, -1, 2, -2, 1, -2, 2, -1, 2, -2, 1, -2, 2, -1, 2, -2, 1, -2, 2, -1, 2, -2, 1, -2, 2, -1, 2, -2, 1, -2, 2, -1, 2, -2, 1, -2, 2, -1, 2, -2, 1, -2, 2, -1, 2, -2, 1, -2, 2, -1, 2, -2, 1, -2
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OFFSET
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0,2
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LINKS
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FORMULA
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G.f.: (1-2*x+2*x^2)/(x+1)/(x^2-x+1). - R. J. Mathar, Nov 14 2007
a(n) + a(n-3) = 0 for n>2.
a(n) = (5*cos(n*Pi)-2*cos(n*Pi/3))/3. (End)
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MAPLE
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MATHEMATICA
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PROG
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CROSSREFS
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KEYWORD
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sign,easy
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AUTHOR
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STATUS
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approved
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