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 A102560 #27 Dec 14 2023 05:17:59
%S A102560 1,0,0,-1,1,0,0,-1,1,0,0,-1,1,0,0,-1,1,0,0,-1,1,0,0,-1,1,0,0,-1,1,0,0,
%T A102560 -1,1,0,0,-1,1,0,0,-1,1,0,0,-1,1,0,0,-1,1,0,0,-1,1,0,0,-1,1,0,0,-1,1,
%U A102560 0,0,-1,1,0,0,-1,1,0,0,-1,1,0,0,-1,1,0,0,-1,1,0,0,-1,1,0,0,-1,1,0,0,-1,1,0,0,-1,1,0,0,-1,1,0,0,-1,1,0,0,-1,1
%N A102560 Expansion of (1-x^3)/(1-x^4).
%C A102560 Period 4: repeat [1, 0, 0, -1].
%H A102560 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (-1,-1,-1).
%F A102560 G.f.: (1+x+x^2)/(1+x+x^2+x^3).
%F A102560 a(n) = (-1)^floor(n/2)/2+(-1)^n/2.
%F A102560 a(n) = cos(Pi*n/2)/2 + sin(Pi*n/2)/2 + cos(Pi*n)/2.
%F A102560 a(n) = -a(n-1)-a(n-2)-a(n-3) for n>2 with a(0)=1, a(1)=a(2)=0. - _Jaume Oliver Lafont_, Dec 05 2008
%p A102560 seq(op([1, 0, 0, -1]), n=0..50); # _Wesley Ivan Hurt_, Jul 06 2016
%t A102560 CoefficientList[ Series[(1 - x^3)/(1 - x^4), {x, 0, 105}], x] (* _Robert G. Wilson v_, Jan 15 2005 *)
%o A102560 (Magma) &cat [[1, 0, 0, -1]^^30]; // _Wesley Ivan Hurt_, Jul 06 2016
%o A102560 (PARI) x='x+O('x^50); Vec((1 - x^3)/(1 - x^4)) \\ _G. C. Greubel_, Jun 02 2017
%K A102560 easy,sign
%O A102560 0,1
%A A102560 _Paul Barry_, Jan 14 2005