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A026037
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a(n) = dot_product(1,2,...,n)*(3,4,...,n,1,2).
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4
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11, 22, 40, 67, 105, 156, 222, 305, 407, 530, 676, 847, 1045, 1272, 1530, 1821, 2147, 2510, 2912, 3355, 3841, 4372, 4950, 5577, 6255, 6986, 7772, 8615, 9517, 10480, 11506, 12597, 13755, 14982, 16280, 17651, 19097, 20620, 22222, 23905, 25671, 27522, 29460, 31487, 33605, 35816, 38122, 40525, 43027
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OFFSET
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3,1
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LINKS
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FORMULA
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G.f.: -x^3*(-11 + 22*x - 18*x^2 + 5*x^3) / (x - 1)^4 . - R. J. Mathar, Apr 17 2011
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MATHEMATICA
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LinearRecurrence[{4, -6, 4, -1}, {11, 22, 40, 67}, 50] (* Vincenzo Librandi, Jun 20 2012 *)
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PROG
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(Magma) I:=[11, 22, 40, 67]; [n le 4 select I[n] else 4*Self(n-1)-6*Self(n-2)+4*Self(n-3)-Self(n-4): n in [1..50]]; // Vincenzo Librandi, Jun 20 2012
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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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