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A117373
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Expansion of (1 - 3x)/(1 - x + x^2).
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12
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1, -2, -3, -1, 2, 3, 1, -2, -3, -1, 2, 3, 1, -2, -3, -1, 2, 3, 1, -2, -3, -1, 2, 3, 1, -2, -3, -1, 2, 3, 1, -2, -3, -1, 2, 3, 1, -2, -3, -1, 2, 3, 1, -2, -3, -1, 2, 3, 1, -2, -3, -1, 2, 3, 1
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OFFSET
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0,2
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COMMENTS
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Row sums of number triangle A117372.
Periodic sequence with period {1, -2, -3, -1, 2, 3}. - Philippe Deléham, Nov 03 2008
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LINKS
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FORMULA
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G.f.: (1 - 3x)/(1 - x + x^2).
a(n) = Sum_{k=0..n} (-1)^(n-k)*(C(k,n-k) + 3*C(k, n-k-1)).
a(n) = ((n mod 3)^2 - 4*(n mod 3) + 1)*(-1)^floor(n/3). - Luce ETIENNE, Nov 18 2017
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MATHEMATICA
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PROG
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(PARI) Vec((1-3*x)/(1-x+x^2) + O(x^90)) \\ Michel Marcus, Apr 06 2016
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CROSSREFS
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KEYWORD
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easy,sign
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AUTHOR
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STATUS
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approved
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