The OEIS is supported by the many generous donors to the OEIS Foundation.
%I #4 Jan 14 2013 05:19:25
%S 0,7,94,1198,15181,191832,2420113,30504742,384323166,4840824840,
%T 60965809190,767757426068,9668215933583,121747651964992,
%U 1533100467093783,19305382814565606,243100053770292709,3061195602161506408
%N Number of nX4 arrays of occupancy after each element moves to some horizontal or antidiagonal neighbor, with no 2-loops and with no occupancy greater than 2
%C Column 4 of A221388
%H R. H. Hardin, <a href="/A221384/b221384.txt">Table of n, a(n) for n = 1..20</a>
%e Some solutions for n=3
%e ..0..1..2..0....0..2..2..1....0..2..2..0....0..2..2..1....0..1..1..1
%e ..0..2..1..1....1..2..2..1....0..2..2..0....0..1..2..1....0..1..2..1
%e ..1..2..2..0....0..0..1..0....1..2..1..0....1..1..1..0....1..2..2..0
%K nonn
%O 1,2
%A _R. H. Hardin_ Jan 14 2013