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%I #4 Jan 22 2013 19:32:36
%S 4,52,540,6188,71310,824144,9525048,110070012,1271809066,14694217628,
%T 169767833676,1961352594276,22659537510670,261784302805272,
%U 3024367348612856,34940131867655732,403658398327592910
%N Number of nX4 arrays of occupancy after each element stays put or moves to some horizontal, diagonal or antidiagonal neighbor, with every occupancy equal to zero or two
%C Column 4 of A221728
%H R. H. Hardin, <a href="/A221727/b221727.txt">Table of n, a(n) for n = 1..29</a>
%e Some solutions for n=3
%e ..0..2..2..0....2..0..0..2....0..0..2..2....2..2..0..0....0..2..0..2
%e ..0..0..0..2....2..2..2..2....0..2..2..2....2..2..2..0....0..2..2..0
%e ..2..2..2..0....0..0..0..0....2..0..0..0....0..0..2..0....2..0..0..2
%K nonn
%O 1,1
%A _R. H. Hardin_ Jan 22 2013