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A187107
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Number of nontrivial compositions of differential operations and directional derivative of the n-th order on the space R^9.
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1
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8, 8, 9, 10, 12, 15, 20, 28, 41, 62, 96, 151, 240, 384, 617, 994, 1604, 2591, 4188, 6772, 10953, 17718, 28664, 46375, 75032, 121400, 196425, 317818, 514236, 832047, 1346276, 2178316, 3524585, 5702894, 9227472, 14930359, 24157824, 39088176
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OFFSET
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1,1
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LINKS
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FORMULA
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a(n) = 2*a(n-1)-a(n-3). G.f.: -x*(7*x^2+8*x-8) / ((x-1)*(x^2+x-1)). [Colin Barker, Dec 14 2012]
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MATHEMATICA
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LinearRecurrence[{2, 0, -1}, {8, 8, 9}, 50] (* Harvey P. Dale, Jul 10 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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