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A033566
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a(n) = (2*n+1) * (4*n-1).
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8
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-1, 9, 35, 77, 135, 209, 299, 405, 527, 665, 819, 989, 1175, 1377, 1595, 1829, 2079, 2345, 2627, 2925, 3239, 3569, 3915, 4277, 4655, 5049, 5459, 5885, 6327, 6785, 7259, 7749, 8255, 8777, 9315, 9869, 10439, 11025, 11627, 12245, 12879, 13529, 14195, 14877, 15575, 16289, 17019, 17765
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listen;
history;
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OFFSET
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0,2
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LINKS
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FORMULA
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G.f.: (-1 + 12*x + 5*x^2)/(1-x)^3.
E.g.f.: (-1 + 10*x + 8*x^2)*exp(x). (End)
Sum_{n>=0} 1/a(n) = -2/3 +log(2)/6-Pi/12 = -0.81294152437.. - R. J. Mathar, May 07 2024
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MAPLE
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MATHEMATICA
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Table[(2*n+1)*(4*n-1), {n, 0, 50}] (* G. C. Greubel, Oct 12 2019 *)
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PROG
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(Magma) [(2*n+1)*(4*n-1): n in [0..50]] # G. C. Greubel, Oct 12 2019
(Sage) [(2*n+1)*(4*n-1) for n in range(50)] # G. C. Greubel, Oct 12 2019
(GAP) List([0..50], n-> (2*n+1)*(4*n-1)); # G. C. Greubel, Oct 12 2019
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CROSSREFS
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KEYWORD
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sign,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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