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 A199933 #23 Jan 05 2025 19:51:39
%S A199933 1,1,-4,0,20,-25,-71,216,94,-1220,1037,4941,-11440,-11008,72112,
%T A199933 -33453,-326675,577060,950750,-4129272,279257,20740793,-27217100,
%U A199933 -72078336,228625372,83808415,-1271796511,1153458144,5060707454,-12183603100,-10694679515,75519944325,-39290857304,-336819940736
%N A199933 Trisection 0 of A199744.
%H A199933 Colin Barker, <a href="/A199933/b199933.txt">Table of n, a(n) for n = 0..1000</a>
%H A199933 Hirschhorn, Michael D., <a href="https://web.archive.org/web/2024*/https://www.fq.math.ca/43-4.html">Non-trivial intertwined second-order recurrence relations</a>, Fibonacci Quart. 43 (2005), no. 4, 316-325. See p. 324.
%H A199933 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (-1,-5,1,-1).
%F A199933 From _Colin Barker_, Dec 27 2017: (Start)
%F A199933 G.f.: (1 + 2*x + 2*x^2) / (1 + x + 5*x^2 - x^3 + x^4).
%F A199933 a(n) = -a(n-1) - 5*a(n-2) + a(n-3) - a(n-4) for n>3.
%F A199933 (End)
%t A199933 CoefficientList[ Series[(1 +2x +2x^2)/(1 +x +5x^2 -x^3 +x^4), {x, 0, 33}], x] (* or *)
%t A199933 LinearRecurrence[{-1, -5, 1, -1}, {1, 1, -4, 0}, 33] (* _Robert G. Wilson v_, Dec 27 2017 *)
%o A199933 (PARI) Vec((1 + 2*x + 2*x^2) / (1 + x + 5*x^2 - x^3 + x^4) + O(x^40)) \\ _Colin Barker_, Dec 27 2017
%K A199933 sign,easy
%O A199933 0,3
%A A199933 _N. J. A. Sloane_, Nov 12 2011