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 A326694 #11 Jan 26 2020 01:07:11 %S A326694 0,0,0,0,0,1,1,1,1,0,1,2,3,3,4,5,6,7,6,5,5,5,4,5,6,6,5,6,5,4,4,3,4,4, %T A326694 4,3,4,5,4,3,3,3,3,3,4,4,4,4,3,4,5,6,6,7,8,9,10,9,8,8,7,8,8,7,8,7,6,6, %U A326694 6,5,6,7,7,7,6,7,8,7,6,6,5,6,6,5,6,5,4 %N A326694 Langton's ant with three cell colors: number of gray cells after n moves of the ant. %C A326694 On a white square, turn 90 degrees right, change the color to black, then move forward one unit. %C A326694 On a black square, turn 90 degrees left, change the color to gray, then move forward one unit. %C A326694 On a gray square, turn 180 degrees, change the color to white, then move forward one unit. %H A326694 Felix Fröhlich, <a href="/A326693/a326693.pdf">Illustration of iterations 0-50</a>, 2019. %F A326694 a(n+276) = a(n). - _Rémy Sigrist_, Jul 19 2019 %e A326694 See illustrations in Fröhlich, 2019. %Y A326694 Cf. A325953, A325954, A325955, A326693, A326695. %K A326694 nonn %O A326694 0,12 %A A326694 _Felix Fröhlich_, Jul 19 2019 %E A326694 More terms from _Rémy Sigrist_, Jul 19 2019