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%I #16 Sep 08 2022 08:44:54
%S 1,10,401,4020,161201,1616030,64802401,649640040,26050404001,
%T 261153680050,10472197606001,104983129740060,4209797387208401,
%U 42202957001824070,1692328077460171201,16965483731603536080,680311677341601614401,6820082257147619680090
%N Denominators of continued fraction convergents to sqrt(404).
%H Vincenzo Librandi, <a href="/A041767/b041767.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 (0,402,0,-1).
%F G.f.: -(x^2-10*x-1) / ((x^2-20*x-1)*(x^2+20*x-1)). - _Colin Barker_, Nov 24 2013
%F a(n) = 402*a(n-2) - a(n-4) for n>3. - _Vincenzo Librandi_, Dec 24 2013
%t Denominator[Convergents[Sqrt[404], 30]] (* _Vincenzo Librandi_, Dec 24 2013 *)
%o (Magma) I:=[1,10,401,4020]; [n le 4 select I[n] else 402*Self(n-2)-Self(n-4): n in [1..40]]; // _Vincenzo Librandi_, Dec 24 2013
%Y Cf. A041766, A040383.
%K nonn,frac,easy
%O 0,2
%A _N. J. A. Sloane_.
%E More terms from _Colin Barker_, Nov 24 2013
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