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A008617
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Expansion of 1/((1-x^2)(1-x^7)).
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9
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1, 0, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 2, 1, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 3, 2, 3, 2, 3, 3, 3, 3, 3, 3, 3, 3, 4, 3, 4, 3, 4, 3, 4, 4, 4, 4, 4, 4, 4, 4, 5, 4, 5, 4, 5, 4, 5, 5, 5, 5, 5, 5, 5, 5, 6, 5, 6, 5, 6, 5, 6, 6
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OFFSET
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0,15
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COMMENTS
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a(n) is the number of (n+9)-digit fixed points under the base-5 Kaprekar map A165032 (see A165036 for the list of fixed points). - Joseph Myers, Sep 04 2009
It appears that this is the number of partitions of 4*n that are 8-term arithmetic progressions. Further, it seems that a(n)=[n/2]-[3n/7]. - John W. Layman, Feb 21 2012
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REFERENCES
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D. J. Benson, Polynomial Invariants of Finite Groups, Cambridge, 1993, p. 100.
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LINKS
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FORMULA
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a(n) = floor((2*n+21+7*(-1)^n)/28). - Tani Akinari, May 19 2014
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MATHEMATICA
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CoefficientList[Series[1 / ((1 - x^2) (1 - x^7)), {x, 0, 100}], x] (* Vincenzo Librandi, Jun 22 2013 *)
LinearRecurrence[{0, 1, 0, 0, 0, 0, 1, 0, -1}, {1, 0, 1, 0, 1, 0, 1, 1, 1}, 80] (* Harvey P. Dale, May 18 2018 *)
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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