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 A128016 #13 Dec 14 2023 05:20:44
%S A128016 1,1,2,2,1,1,-1,-1,-2,-2,-1,-1,1,1,2,2,1,1,-1,-1,-2,-2,-1,-1,1,1,2,2,
%T A128016 1,1,-1,-1,-2,-2,-1,-1,1,1,2,2,1,1,-1,-1,-2,-2,-1,-1,1,1,2,2,1,1,-1,
%U A128016 -1,-2,-2,-1,-1,1,1,2,2,1,1,-1,-1,-2,-2,-1,-1
%N A128016 Expansion of (1+x+x^2+x^3)/(1-x^2+x^4).
%C A128016 Periodic{1,1,2,2,1,1,-1,-1,-2,-2,-1,-1}.
%H A128016 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,1,0,-1).
%F A128016 G.f.: (1-x^4)/(1-x-x^2+x^3+x^4-x^5); a(n)=cos(5*pi*n/6)/2+(1-sqrt(3)/2)sin(5*pi*n/6)+cos(pi*n/6)/2+(1+sqrt(3)/2)sin(pi*n/6);
%t A128016 CoefficientList[Series[(1+x+x^2+x^3)/(1-x^2+x^4),{x,0,100}],x] (* or *) LinearRecurrence[{0,1,0,-1},{1,1,2,2},100] (* _Harvey P. Dale_, Aug 02 2015 *)
%Y A128016 Cf. A128017.
%K A128016 easy,sign
%O A128016 0,3
%A A128016 _Paul Barry_, Feb 11 2007