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 A131290 #33 Dec 12 2023 09:24:45
%S A131290 1,3,2,0,-1,0,2,3,2,0,-1,0,2,3,2,0,-1,0,2,3,2,0,-1,0,2,3,2,0,-1,0,2,3,
%T A131290 2,0,-1,0,2,3,2,0,-1,0,2,3,2,0,-1,0,2,3,2,0,-1,0,2,3,2,0,-1,0,2,3,2,0,
%U A131290 -1,0,2,3,2,0,-1,0,2,3,2,0,-1,0,2,3,2,0,-1,0,2,3,2,0,-1,0,2,3,2,0,-1,0,2,3,2,0,-1
%N A131290 1 followed by period 6: repeat [3, 2, 0, -1, 0, 2].
%H A131290 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (2,-2,1).
%F A131290 G.f.: (1+x-2*x^2+x^3)/((1-x)*(1-x+x^2)). - _R. J. Mathar_, Feb 27 2008
%F A131290 If n mod 6 = 4 then a(n) = (Fibonacci(n-3)*Fibonacci(n+1)) mod 4 -2, else a(n) = (Fibonacci(n-3)*Fibonacci(n+1)) mod 4, n>0. - _Gary Detlefs_, Dec 12 2010
%F A131290 From _Wesley Ivan Hurt_, Jun 20 2016: (Start)
%F A131290 a(n) = 2*a(n-1) - 2*a(n-2) + a(n-3) for n>4.
%F A131290 a(0) = 1, a(n) = 1 + cos(n*Pi/3) + sqrt(3)*sin(n*Pi/3) for n>0. (End)
%p A131290 A131290 := proc(n) if n = 0 then 1; else op(((n-1)mod 6)+1,[3,2,0,-1,0,2]) ; fi ; end: seq(A131290(n),n=0..100) ; # _R. J. Mathar_, Feb 27 2008
%t A131290 PadRight[{1},110,{2,3,2,0,-1,0}] (* or *) Join[{1},LinearRecurrence[ {2,-2,1},{3,2,0},110]] (* _Harvey P. Dale_, Jun 22 2012 *)
%o A131290 (Magma) [1] cat &cat [[3, 2, 0, -1, 0, 2]^^30]; // _Wesley Ivan Hurt_, Jun 20 2016
%Y A131290 Cf. A079757, A100219, A130869.
%K A131290 sign,easy
%O A131290 0,2
%A A131290 _Paul Curtz_, Sep 29 2007
%E A131290 More terms from _R. J. Mathar_, Feb 27 2008