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 A131017 #17 Dec 12 2023 09:33:53
%S A131017 1,1,2,-1,2,1,1,1,2,-1,2,1,1,1,2,-1,2,1,1,1,2,-1,2,1,1,1,2,-1,2,1,1,1,
%T A131017 2,-1,2,1,1,1,2,-1,2,1,1,1,2,-1,2,1,1,1,2,-1,2,1,1,1,2,-1,2,1,1,1,2,
%U A131017 -1,2,1,1,1,2,-1,2,1,1,1,2,-1,2,1,1,1,2,-1,2,1,1,1,2,-1,2,1,1,1,2,-1,2,1,1,1,2,-1,2,1,1,1,2,-1,2,1,1,1,2,-1,2,1,1,1,2
%N A131017 Period 6: repeat [1, 1, 2, -1, 2, 1].
%H A131017 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,0,0,1).
%F A131017 |a(n)| = A131718(n).
%F A131017 a(n) = A131717(n+1) - A131717(n).
%F A131017 O.g.f.: (1+x+2*x^2-x^3+2*x^4+x^5)/((1-x)*(1+x)*(x^2+x+1)*(x^2-x+1)). - _R. J. Mathar_, Jul 07 2008
%F A131017 a(n) = (3+2*(-1)^n+cos(n*Pi/3)-3*cos(n*Pi/3)^2+3*sin(n*Pi/3)^2)/3. - _Wesley Ivan Hurt_, Jun 24 2022
%t A131017 Flatten[Table[{1, 1, 2, -1, 2, 1}, {20}]] (* _Wesley Ivan Hurt_, Jun 24 2022 *)
%t A131017 PadRight[{},120,{1,1,2,-1,2,1}] (* _Harvey P. Dale_, Oct 10 2023 *)
%Y A131017 Cf. A131717, A131718.
%K A131017 sign,easy
%O A131017 0,3
%A A131017 _Paul Curtz_, Sep 23 2007
%E A131017 Edited by _R. J. Mathar_, Jul 07 2008