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7, 8, 9, 12, 16, 21, 29, 41, 58, 83, 120, 174, 253, 369, 539, 788, 1153, 1688, 2472, 3621, 5305, 7773, 11390, 16691, 24460, 35846, 52533, 76989, 112831, 165360, 242345, 355172, 520528, 762869, 1118037
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refs;
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OFFSET
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0,1
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LINKS
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FORMULA
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G.f.: (7-6*x-5*x^3)/(1-2*x+x^2-x^3+x^4). - Colin Barker, Dec 30 2011
a(n) = a(n-1) + a(n-3) - 4 for n>2. - Greg Dresden, Feb 09 2020
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MATHEMATICA
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CoefficientList[Series[(7 - 6*x - 5*x^3)/(1 - 2*x + x^2 - x^3 + x^4), {x, 0, 50}], x] (* G. C. Greubel, Apr 26 2017 *)
LinearRecurrence[{2, -1, 1, -1}, {7, 8, 9, 12}, 40] (* Harvey P. Dale, Aug 07 2021 *)
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PROG
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(PARI) x='x+O('x^50); Vec((7 - 6*x - 5*x^3)/(1 - 2*x + x^2 - x^3 + x^4)) \\ G. C. Greubel, Apr 26 2017
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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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