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A159287
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Expansion of x^2/(1-x^2-2*x^3).
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7
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0, 0, 1, 0, 1, 2, 1, 4, 5, 6, 13, 16, 25, 42, 57, 92, 141, 206, 325, 488, 737, 1138, 1713, 2612, 3989, 6038, 9213, 14016, 21289, 32442, 49321, 75020, 114205, 173662, 264245, 402072, 611569, 930562, 1415713, 2153700, 3276837, 4985126, 7584237, 11538800
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OFFSET
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0,6
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COMMENTS
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A floretion-generated sequence: 'i + 0.5('ij' + 'ik' + 'ji' + 'jk' + 'ki' + 'kj').
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LINKS
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FORMULA
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G.f.: x^2/(1-x^2-2*x^3).
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MATHEMATICA
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CoefficientList[Series[x^2/(1-x^2-2x^3), {x, 0, 50}], x] (* Harvey P. Dale, May 29 2021 *)
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PROG
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(Magma) I:=[0, 0, 1]; [n le 3 select I[n] else Self(n-2) + 2*Self(n-3): n in [1..30]]; // G. C. Greubel, Jun 27 2018
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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