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 A166446 #17 Sep 08 2022 08:45:48
%S A166446 1,1,1,1,0,0,-1,-1,-1,-1,0,0,1,1,1,1,0,0,-1,-1,-1,-1,0,0,1,1,1,1,0,0,
%T A166446 -1,-1,-1,-1,0,0,1,1,1,1,0,0,-1,-1,-1,-1,0,0,1,1,1,1,0,0,-1,-1,-1,-1,
%U A166446 0,0,1,1,1,1,0,0,-1,-1,-1,-1,0,0,1,1,1,1,0,0
%N A166446 Period 12: repeat [1,1,1,1,0,0,-1,-1,-1,-1,0,0].
%C A166446 a(n+2) is the Hankel transform of A110199. - _Paul Barry_, Jun 23 2010
%H A166446 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,1,0,-1).
%F A166446 G.f.: (1+x)/(1-x^2+x^4).
%F A166446 a(n) = a(n-2)-a(n-4). - _Wesley Ivan Hurt_, May 09 2021
%t A166446 LinearRecurrence[{0,1,0,-1}, {1,1,1,1}, 50] (* _G. C. Greubel_, May 14 2016 *)
%o A166446 (Magma) &cat [[1,1,1,1,0,0,-1,-1,-1,-1,0,0]^^10]; // _Vincenzo Librandi_, May 15 2016
%Y A166446 Cf. A010892 (bisection).
%K A166446 easy,sign
%O A166446 0,1
%A A166446 _Paul Barry_, Oct 13 2009
%E A166446 Incorrect comment removed - _R. J. Mathar_, Oct 02 2012