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 A131193 #14 Dec 12 2023 09:26:32
%S A131193 0,1,-3,3,-1,0,0,1,-3,3,-1,0,0,1,-3,3,-1,0,0,1,-3,3,-1,0,0,1,-3,3,-1,
%T A131193 0,0,1,-3,3,-1,0,0,1,-3,3,-1,0,0,1,-3,3,-1,0,0,1,-3,3,-1,0,0,1,-3,3,
%U A131193 -1,0,0,1,-3,3,-1,0,0,1,-3,3,-1,0,0,1,-3,3,-1,0,0,1,-3,3,-1,0
%N A131193 Period 6: repeat [0, 1, -3, 3, -1, 0].
%H A131193 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (-1,-1,-1,-1,-1).
%F A131193 G.f.: x*(x-1)^2/((x+1)*(x^2-x+1)*(x^2+x+1)). - _R. J. Mathar_, Nov 14 2007
%F A131193 From _Wesley Ivan Hurt_, Jun 20 2016: (Start)
%F A131193 a(n) + a(n-1) + a(n-2) + a(n-3) + a(n-4) + a(n-5) = 0 for n>4.
%F A131193 a(n) = sin(n*Pi/6) * (2*sqrt(3)*cos(n*Pi/6) + 3*sqrt(3)*cos(n*Pi/2) - sin(n*Pi/2) + 8*sin(5*n*Pi/6))/3. (End)
%p A131193 A131193:=n->[0, 1, -3, 3, -1, 0][(n mod 6)+1]: seq(A131193(n), n=0..100); # _Wesley Ivan Hurt_, Jun 20 2016
%t A131193 PadRight[{}, 100, {0, 1, -3, 3, -1, 0}] (* _Wesley Ivan Hurt_, Jun 20 2016 *)
%o A131193 (Magma) &cat [[0, 1, -3, 3, -1, 0]^^20]; // _Wesley Ivan Hurt_, Jun 20 2016
%K A131193 sign,easy
%O A131193 0,3
%A A131193 _Paul Curtz_, Sep 26 2007