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A123005
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Expansion of g.f. x^2/(1-2*x-49*x^2).
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4
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0, 1, 2, 53, 204, 3005, 16006, 179257, 1142808, 11069209, 78136010, 698663261, 5225991012, 44686481813, 345446523214, 2880530655265, 22687940948016, 186521884004017, 1484752874460818, 12109078065118469, 96971046978817020
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OFFSET
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1,3
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REFERENCES
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Jay Kappraff, Beyond Measure, A Guided Tour Through Nature, Myth and Number, World Scientific, 2002.
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LINKS
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FORMULA
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a(n) = 2*a(n-1) +49*a(n-2).
a(n) = (7*i)^(n-2)*ChebyshevU(n-2, -i/7). - G. C. Greubel, Jul 12 2021
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MATHEMATICA
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CoefficientList[Series[x^2/(1-2x-49x^2), {x, 0, 30}], x] (* Harvey P. Dale, Apr 12 2020 *
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PROG
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(Magma) I:=[0, 1]; [n le 2 select I[n] else 2*Self(n-1) -49*Self(n-2): n in [1..31]]; // G. C. Greubel, Jul 12 2021
(Sage) [(7*i)^(n-2)*chebyshev_U(n-2, -i/7) for n in [1..30]] # G. C. Greubel, Jul 12 2021
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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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Definition replaced by generating function - the Assoc. Eds. of the OEIS, Mar 27 2010
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STATUS
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approved
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