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A006137
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a(n) = 1 + n/2 + 9*n^2/2.
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5
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1, 6, 20, 43, 75, 116, 166, 225, 293, 370, 456, 551, 655, 768, 890, 1021, 1161, 1310, 1468, 1635, 1811, 1996, 2190, 2393, 2605, 2826, 3056, 3295, 3543, 3800, 4066, 4341, 4625, 4918, 5220, 5531, 5851, 6180, 6518, 6865, 7221, 7586, 7960, 8343, 8735, 9136, 9546
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OFFSET
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0,2
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COMMENTS
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LINKS
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FORMULA
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O.g.f.: (1 + 3*x+ 5*x^2)/(1 - x)^3.
E.g.f.: exp(x)*(2 + 10*x + 9*x^2)/2. (End)
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MATHEMATICA
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Table[1+n/2+9 n^2/2, {n, 0, 40}] (* or *) LinearRecurrence[{3, -3, 1}, {1, 6, 20}, 40] (* Harvey P. Dale, Oct 05 2012 *)
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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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