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 A326693 #14 Jan 26 2020 01:07:15 %S A326693 0,1,2,3,4,3,4,5,6,6,5,4,3,4,3,2,1,0,0,0,1,2,2,1,0,1,1,0,0,0,1,1,0,1, %T A326693 2,2,1,0,0,0,1,2,3,4,3,4,5,6,6,5,4,3,4,3,2,1,0,0,0,1,1,0,1,1,0,0,0,1, %U A326693 2,2,1,0,1,2,2,1,0,0,0,1,1,0,1,1,0,0,0 %N A326693 Langton's ant with three cell colors: number of black cells after n moves of the ant. %C A326693 On a white square, turn 90 degrees right, change the color to black, then move forward one unit. %C A326693 On a black square, turn 90 degrees left, change the color to gray, then move forward one unit. %C A326693 On a gray square, turn 180 degrees, change the color to white, then move forward one unit. %C A326693 The complete configuration, including the position and direction of the ant and the color of all cells, has period 276. - _Rémy Sigrist_, Jul 19 2019 %H A326693 Felix Fröhlich, <a href="/A326693/a326693.pdf">Illustration of iterations 0-50</a>, 2019. %F A326693 a(n+276) = a(n). - _Rémy Sigrist_, Jul 19 2019 %e A326693 See illustrations in Fröhlich, 2019. %Y A326693 Cf. A325953, A325954, A325955, A326694, A326695. %K A326693 nonn %O A326693 0,3 %A A326693 _Felix Fröhlich_, Jul 19 2019 %E A326693 More terms from _Rémy Sigrist_, Jul 19 2019