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A034721
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a(n) = (10*n^3 - 9*n^2 + 2*n)/3 + 1.
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1
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1, 2, 17, 66, 169, 346, 617, 1002, 1521, 2194, 3041, 4082, 5337, 6826, 8569, 10586, 12897, 15522, 18481, 21794, 25481, 29562, 34057, 38986, 44369, 50226, 56577, 63442, 70841, 78794, 87321, 96442, 106177, 116546, 127569, 139266, 151657
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internal format)
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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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a(n) = A034720(n) + 1 for n > 0, where +1 counts the empty string.
E.g.f.: (3 + 3*x + 21*x^2 + 10*x^3)*exp(x)/3. - G. C. Greubel, Nov 11 2019
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MAPLE
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seq((10*n^3 -9*n^2 +2*n +3)/3, n=0..40); # G. C. Greubel, Nov 11 2019
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MATHEMATICA
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LinearRecurrence[{4, -6, 4, -1}, {1, 2, 17, 66}, 40] (* Vincenzo Librandi, Jun 21 2012 *)
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PROG
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(Magma) I:=[1, 2, 17, 66]; [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..40]]; // Vincenzo Librandi, Jun 21 2012
(Sage) [(10*n^3 -9*n^2 +2*n +3)/3 for n in (0..40)] # G. C. Greubel, Nov 11 2019
(GAP) List([0..40], n-> (10*n^3 -9*n^2 +2*n +3)/3); # G. C. Greubel, Nov 11 2019
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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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EXTENSIONS
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STATUS
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approved
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