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 A275117 #21 May 29 2021 02:12:13 %S A275117 1,2,4,3,1,3,1,2,4,3,4,3,1,2,4,2,1,3,4,3,4,3,1,2,4,2,4,3,1,2,1,3,4,2, %T A275117 4,2,4,3,1,2,1,2,4,3,1,3,4,2,1,2,1,3,1,2,1,2,4,3,1,3,4,2,1,2,1,2,4,3, %U A275117 1,3,1,2,4,3,4,2,1,3,1,3,1,2,4,3,4,3,1 %N A275117 Direction where Langton's ant is looking after n moves: 1 if looking in starting direction, 2 if looking 90 degrees clockwise from starting direction, 3 if looking 90 degrees counterclockwise from starting direction, or 4 if looking in direction opposite to starting direction. %F A275117 From _Andrey Zabolotskiy_, Oct 11 2016: (Start) %F A275117 Let d(n) = (A255938(n) mod 4). Then: %F A275117 a(n)=1 if d(n)=0, %F A275117 a(n)=2 if d(n)=1, %F A275117 a(n)=4 if d(n)=2, %F A275117 a(n)=3 if d(n)=3. %F A275117 (End) %Y A275117 Cf. A102358, A102369, A204810, A255938, A261990, A269757. %K A275117 nonn %O A275117 0,2 %A A275117 _Felix Fröhlich_, Jul 18 2016 %E A275117 More terms from _Andrey Zabolotskiy_, Oct 11 2016