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A123006
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Expansion of x^2/(1 -2*x -121*x^2).
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3
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0, 1, 2, 125, 492, 16109, 91750, 2132689, 15367128, 288789625, 2437001738, 39817548101, 374512306500, 5566947933221, 56449884952942, 786500469825625, 8403437018957232, 111973430886815089, 1240762741067455250
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OFFSET
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1,3
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LINKS
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FORMULA
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a(n) = 2*a(n-1) + 121*a(n-2).
a(n) = (11*i)^(n-2)*ChebyshevU(n-2, -i/11). - G. C. Greubel, Jul 12 2021
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MATHEMATICA
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Rest@CoefficientList[Series[x^2/(1 -2*x -121*x^2), {x, 0, 30}], x]
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PROG
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(Magma) [n le 2 select n-1 else 2*Self(n-1) + 121*Self(n-2): n in [1..30]]; // G. C. Greubel, Jul 12 2021
(Sage) [(11*i)^(n-2)*chebyshev_U(n-2, -i/11) 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
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AUTHOR
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STATUS
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approved
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