A261990 - OEIS

%I #20 Apr 07 2020 22:57:28

%S 0,0,0,0,1,0,0,0,0,1,0,0,0,0,1,1,1,1,0,1,0,0,0,0,1,0,0,0,0,1,1,1,1,0,

%T 1,0,0,0,0,1,0,0,0,0,1,1,1,1,0,1,1,0,0,1,0,0,0,0,1,1,1,1,0,1,0,0,0,0,

%U 1,0,0,0,0,1,1,1,1,0,1,0,0,0,0,1,0,0,0,0,1,1,1,1,0,1,1,0,0,0,0,1,1,0,1,0,0,0,0

%N Color of the cell Langton's Ant touches on its n-th step before the color is changed by the ant; 0=white, 1=black.

%C The ant starts from a completely white grid.

%C There are never more than four 0's or 1's in a row because four identical turns will circle back into the same cell, which will have since changed.

%C The sequence begins repeating at the 9977th step, in a cycle of length 104.

%H Aaron David Fairbanks, <a href="/A261990/b261990.txt">Table of n, a(n) for n = 0..10287</a>

%H Wikipedia, <a href="http://en.wikipedia.org/wiki/Langton%27s_ant">Langton's Ant</a>

%e On the 0th step, the ant lands on a white square and turns it black. On the 1st step, it lands on another white square. On the 4th step, it lands on a black square, etc.

%Y Cf. A126978.

%K easy,nonn

%O 0

%A _Aaron David Fairbanks_, Sep 07 2015