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A008130
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a(n) = floor(n/3)*ceiling(n/3).
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2
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0, 0, 0, 1, 2, 2, 4, 6, 6, 9, 12, 12, 16, 20, 20, 25, 30, 30, 36, 42, 42, 49, 56, 56, 64, 72, 72, 81, 90, 90, 100, 110, 110, 121, 132, 132, 144, 156, 156, 169, 182, 182, 196, 210, 210, 225, 240, 240, 256, 272, 272, 289
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OFFSET
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0,5
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LINKS
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FORMULA
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G.f. -x^3*(1+x) / ( (1+x+x^2)^2*(x-1)^3 ). (End)
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MAPLE
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MATHEMATICA
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CoefficientList[Series[- x^3 (1 + x) / ((1 + x + x^2)^2 (x - 1)^3), {x, 0, 60}], x] (* Vincenzo Librandi, Jun 10 2013 *)
LinearRecurrence[{1, 0, 2, -2, 0, -1, 1}, {0, 0, 0, 1, 2, 2, 4}, 60] (* Harvey P. Dale, Dec 31 2016 *)
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PROG
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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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STATUS
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approved
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