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%I #23 Sep 08 2022 08:44:54
%S 1,1,2,3,86,89,175,264,7567,7831,15398,23229,665810,689039,1354849,
%T 2043888,58583713,60627601,119211314,179838915,5154700934,5334539849,
%U 10489240783,15823780632,453555098479,469378879111,922933977590,1392312856701,39907693965218
%N Denominators of continued fraction convergents to sqrt(215).
%H Vincenzo Librandi, <a href="/A041401/b041401.txt">Table of n, a(n) for n = 0..200</a>
%H <a href="/index/Rec#order_08">Index entries for linear recurrences with constant coefficients</a>, signature (0, 0, 0, 88, 0, 0, 0, -1).
%F G.f.: -(x^2-x-1)*(x^4+3*x^2+1) / (x^8-88*x^4+1). - _Colin Barker_, Nov 17 2013
%F a(n) = 88*a(n-4) - a(n-8) for n>7. - _Vincenzo Librandi_, Dec 17 2013
%t Denominator[Convergents[Sqrt[215], 30]] (* _Harvey P. Dale_, Oct 11 2012 *)
%t CoefficientList[Series[(1 + x - x^2) (x^4 + 3 x^2 + 1)/(x^8 - 88 x^4 + 1), {x, 0, 40}], x] (* _Vincenzo Librandi_, Dec 17 2013 *)
%t LinearRecurrence[{0,0,0,88,0,0,0,-1},{1,1,2,3,86,89,175,264},30] (* _Harvey P. Dale_, Dec 25 2019 *)
%o (Magma) I:=[1,1,2,3,86,89,175,264]; [n le 8 select I[n] else 88*Self(n-4)-Self(n-8): n in [1..40]]; // _Vincenzo Librandi_, Dec 17 2013
%Y Cf. A041400, A040200.
%K nonn,frac,easy
%O 0,3
%A _N. J. A. Sloane_.
%E More terms from _Colin Barker_, Nov 17 2013
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