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 A041071 #31 Aug 11 2024 09:55:09
%S A041071 1,2,25,52,649,1350,16849,35048,437425,909898,11356201,23622300,
%T A041071 294823801,613269902,7654062625,15921395152,198710804449,413343004050,
%U A041071 5158826853049,10730996710148,133930787374825,278592571459798,3477041644892401,7232675861244600
%N A041071 Denominators of continued fraction convergents to sqrt(42).
%H A041071 Vincenzo Librandi, <a href="/A041071/b041071.txt">Table of n, a(n) for n = 0..200</a>
%H A041071 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,26,0,-1).
%F A041071 G.f.: -(x^2-2*x-1) / (x^4-26*x^2+1). - _Colin Barker_, Nov 12 2013
%F A041071 a(n) = 26*a(n-2) - a(n-4). - _Vincenzo Librandi_, Dec 10 2013
%t A041071 Table[Denominator[FromContinuedFraction[ContinuedFraction[Sqrt[42],n]]],{n,1,50}] (* _Vladimir Joseph Stephan Orlovsky_, Mar 22 2011 *)
%t A041071 Denominator[Convergents[Sqrt[42], 30]] (* _Vincenzo Librandi_, Dec 10 2013 *)
%t A041071 LinearRecurrence[{0,26,0,-1},{1,2,25,52},30] (* _Harvey P. Dale_, Oct 17 2019 *)
%o A041071 (Magma) I:=[1, 2, 25, 52]; [n le 4 select I[n] else 26*Self(n-2)-Self(n-4): n in [1..30]]; // _Vincenzo Librandi_, Dec 10 2013
%Y A041071 Cf. A010496, A040035, A041070 (numerators).
%K A041071 nonn,cofr,frac,easy
%O A041071 0,2
%A A041071 _N. J. A. Sloane_
%E A041071 More terms from _Colin Barker_, Nov 12 2013