A221831 - OEIS

%I #4 Jan 26 2013 10:43:54

%S 0,64,2930,115417,4715043,192788993,7888216533,322723834959,

%T 13203608881221,540203150208573,22101534579211095,904249026745794715,

%U 36995912673327194833,1513629078095632460534,61927733346071816062294

%N Number of 4Xn arrays of occupancy after each element moves to some horizontal, vertical or antidiagonal neighbor, without 2-loops or left turns

%C Row 4 of A221828

%H R. H. Hardin, <a href="/A221831/b221831.txt">Table of n, a(n) for n = 1..25</a>

%e Some solutions for n=3

%e ..1..1..1....1..1..0....1..1..1....0..2..0....0..3..1....0..2..0....1..1..1

%e ..2..0..1....2..1..1....2..2..0....1..2..0....0..1..1....2..2..0....1..2..0

%e ..1..1..0....1..0..2....2..0..0....0..2..1....1..1..1....2..1..0....1..1..1

%e ..2..1..1....1..1..1....1..1..1....1..3..0....1..2..0....1..1..1....1..2..0

%K nonn

%O 1,2

%A _R. H. Hardin_ Jan 26 2013