This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A041161 #16 Jul 09 2025 00:21:47
%S A041161 1,2,37,76,1405,2886,53353,109592,2026009,4161610,76934989,158031588,
%T A041161 2921503573,6001038734,110940200785,227881440304,4212806126257,
%U A041161 8653493692818,159975692596981,328604878886780
%N A041161 Denominators of continued fraction convergents to sqrt(90).
%H A041161 Vincenzo Librandi, <a href="/A041161/b041161.txt">Table of n, a(n) for n = 0..200</a>
%H A041161 <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (0,38,0,-1).
%F A041161 G.f.: (1 +2*x -x^2)/(x^4 -38*x^2 +1). - _Vincenzo Librandi_, Dec 12 2013
%F A041161 a(n) = 38*a(n-2) - a(n-4), - _Vincenzo Librandi_, Dec 12 2013
%t A041161 Denominator[Convergents[Sqrt[90],30]] (* _Harvey P. Dale_, May 20 2013 *)
%t A041161 CoefficientList[Series[(1 + 2 x - x^2)/(x^4 - 38 x^2 + 1), {x, 0, 30}], x] (* _Vincenzo Librandi_, Dec 12 2013 *)
%o A041161 (Magma) I:=[1, 2, 37, 76]; [n le 4 select I[n] else 38*Self(n-2)-Self(n-4): n in [1..30]]; // _Vincenzo Librandi_, Dec 12 2013
%Y A041161 Cf. A041160.
%K A041161 nonn,frac,easy
%O A041161 0,2
%A A041161 _N. J. A. Sloane_