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%I #17 Jun 26 2022 23:31:07
%S 1,2,13,28,1749,3526,22905,49336,3081737,6212810,40358597,86930004,
%T 5430018845,10946967694,71111825009,153170617712,9567690123153,
%U 19288550864018,125298995307261,269886541478540,16858264566976741,33986415675432022,220776758619568873
%N Denominators of continued fraction convergents to sqrt(990).
%H Vincenzo Librandi, <a href="/A042917/b042917.txt">Table of n, a(n) for n = 0..200</a>
%H <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,1762,0,0,0,-1).
%F G.f.: -(x^2-2*x-1)*(x^4+14*x^2+1) / ((x^4-42*x^2+1)*(x^4+42*x^2+1)). - _Colin Barker_, Dec 25 2013
%F a(n) = 1762*a(n-4) - a(n-8) for n>7. - _Vincenzo Librandi_, Feb 01 2014
%t Denominator[Convergents[Sqrt[990], 30]] (* _Vincenzo Librandi_, Feb 01 2014 *)
%o (Magma) I:=[1,2,13,28,1749,3526,22905,49336]; [n le 8 select I[n] else 1762*Self(n-4)-Self(n-8): n in [1..30]]; // _Vincenzo Librandi_, Feb 01 2014
%Y Cf. A042916, A040958.
%K nonn,frac,easy
%O 0,2
%A _N. J. A. Sloane_
%E More terms from _Colin Barker_, Dec 25 2013
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