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 A041840 #29 Jul 09 2025 01:45:42
%S A041840 21,883,37107,1559377,65530941,2753858899,115727604699,4863313256257,
%T A041840 204374884367493,8588608456690963,360925930065387939,
%U A041840 15167477671202984401,637394988120590732781,26785756978736013761203
%N A041840 Numerators of continued fraction convergents to sqrt(442).
%H A041840 Vincenzo Librandi, <a href="/A041840/b041840.txt">Table of n, a(n) for n = 0..200</a>
%H A041840 Tanya Khovanova, <a href="http://www.tanyakhovanova.com/RecursiveSequences/RecursiveSequences.html">Recursive Sequences</a>
%H A041840 <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (42,1).
%F A041840 G.f.: (21+x)/(1-42*x-x^2). [_Philippe Deléham_, Nov 23 2008]
%F A041840 a(n) = 42*a(n-1)+a(n-2) for n>1, a(0)=21, a(1)=883. [_Philippe Deléham_, Nov 23 2008]
%t A041840 Numerator[Convergents[Sqrt[442], 30]] (* or *) LinearRecurrence[{42, 1}, {21, 883}, 30] (* _Harvey P. Dale_, Nov 20 2012 *)
%t A041840 CoefficientList[Series[(21 + x)/(1 - 42 x - x^2), {x, 0, 25}], x] (* _Vincenzo Librandi_, Nov 10 2013 *)
%Y A041840 Cf. A041841.
%K A041840 nonn,cofr,frac,easy,less
%O A041840 0,1
%A A041840 _N. J. A. Sloane_