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 A159955 #36 Dec 12 2023 08:09:28
%S A159955 0,1,2,1,2,0,2,0,1,0,1,2,1,2,0,2,0,1,0,1,2,1,2,0,2,0,1,0,1,2,1,2,0,2,
%T A159955 0,1,0,1,2,1,2,0,2,0,1,0,1,2,1,2,0,2,0,1,0,1,2,1,2,0,2,0,1,0,1,2,1,2,
%U A159955 0,2,0,1,0,1,2,1,2,0,2,0,1,0,1,2,1,2,0,2,0,1,0,1,2,1,2,0,2,0,1
%N A159955 Period 9: repeat [0, 1, 2, 1, 2, 0, 2, 0, 1].
%H A159955 <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,-1,1,0,-1,1).
%F A159955 a(n+9) = a(n) with a(0) = a(5) = a(7) = 0, a(1) = a(3) = a(8) = 1, a(2) = a(4) = a(6) = 2.
%F A159955 a(n) = floor((4*n-9)/3) mod 3. - _Gary Detlefs_, May 15 2011
%F A159955 a(n) = (n + floor(n/3)) mod 3. - _William Walkington_, Mar 22 2016
%F A159955 From _Chai Wah Wu_, Jul 30 2020: (Start)
%F A159955 a(n) = a(n-1) - a(n-3) + a(n-4) - a(n-6) + a(n-7) for n > 6.
%F A159955 G.f.: x*(-x^5 + x^4 - 2*x^3 + x^2 - x - 1)/((x - 1)*(x^6 + x^3 + 1)). (End)
%t A159955 PadRight[{}, 120, {0, 1, 2, 1, 2, 0, 2, 0, 1}] (* _Vincenzo Librandi_, Mar 24 2016 *)
%o A159955 (Magma) &cat[[0, 1, 2, 1, 2, 0, 2, 0, 1]^^15]; // _Vincenzo Librandi_, Mar 24 2016
%K A159955 easy,nonn
%O A159955 0,3
%A A159955 _Philippe Deléham_, Apr 27 2009