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%I #13 Sep 08 2022 08:45:28
%S 0,1,2,125,492,16109,91750,2132689,15367128,288789625,2437001738,
%T 39817548101,374512306500,5566947933221,56449884952942,
%U 786500469825625,8403437018957232,111973430886815089,1240762741067455250
%N Expansion of x^2/(1 -2*x -121*x^2).
%H G. C. Greubel, <a href="/A123006/b123006.txt">Table of n, a(n) for n = 1..800</a>
%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2, 121).
%F a(n) = 2*a(n-1) + 121*a(n-2).
%F a(n) = (11*i)^(n-2)*ChebyshevU(n-2, -i/11). - _G. C. Greubel_, Jul 12 2021
%t Rest@CoefficientList[Series[x^2/(1 -2*x -121*x^2), {x,0,30}], x]
%o (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
%o (Sage) [(11*i)^(n-2)*chebyshev_U(n-2, -i/11) for n in [1..30]] # _G. C. Greubel_, Jul 12 2021
%Y Sequences of the form (m*i)^(n-1)*ChebyshevU(n-1, -i/m): A131577 (m=0), A000129 (m=1), A085449 (m=2), A002534 (m=3), A161007 (m=4), A123004 (m=5), A123005 (m=7), this sequence (m=11).
%K nonn
%O 1,3
%A _Roger L. Bagula_ and _Gary W. Adamson_, Sep 23 2006
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