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%I #4 Jan 09 2013 16:37:02
%S 1,31,312,3334,38146,431474,4855258,54587829,613235478,6885012344,
%T 77275657244,867163601744,9729984671155,109168050158528,
%U 1224793149317547,13741066811792010,154160315091605934,1729503583940965893
%N Number of nX4 arrays of occupancy after each element moves to some horizontal, vertical or antidiagonal neighbor, with every occupancy equal to zero or two
%C Column 4 of A221308
%H R. H. Hardin, <a href="/A221306/b221306.txt">Table of n, a(n) for n = 1..39</a>
%e Some solutions for n=3
%e ..0..2..2..0....0..0..0..2....2..0..0..0....0..2..0..2....0..0..2..0
%e ..2..0..2..2....2..2..2..2....2..2..2..0....2..0..0..2....2..2..2..0
%e ..0..2..0..0....0..0..0..2....2..0..2..0....0..2..2..0....2..0..2..0
%K nonn
%O 1,2
%A _R. H. Hardin_ Jan 09 2013
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