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A176563
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Period 4: repeat [1, -3, 1, 1].
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1
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1, -3, 1, 1, 1, -3, 1, 1, 1, -3, 1, 1, 1, -3, 1, 1, 1, -3, 1, 1, 1, -3, 1, 1, 1, -3, 1, 1, 1, -3, 1, 1, 1, -3, 1, 1, 1, -3, 1, 1, 1, -3, 1, 1, 1, -3, 1, 1, 1, -3, 1, 1, 1, -3, 1, 1, 1, -3, 1, 1, 1, -3, 1, 1, 1, -3, 1, 1, 1, -3, 1, 1, 1, -3, 1, 1, 1, -3, 1, 1, 1, -3, 1, 1, 1, -3, 1, 1, 1, -3, 1, 1, 1
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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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Sum_{k>=0} a(k)/(k+1) = 0.
a(n) = cos(n*Pi) - 2*sin(n*Pi/2).
G.f.: (1-2*x-x^2)/((1+x)*(1+x^2)).
a(n) = -a(n-1) -a(n-2) -a(n-3) for n>2. [R. J. Mathar, Apr 28 2010]
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MAPLE
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MATHEMATICA
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PROG
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(PARI) a(n)=[1, -3, 1, 1][n%4+1]
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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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