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%I #4 Jan 20 2013 19:59:35
%S 0,4,54,811,11344,160999,2286878,32522604,462463456,6575844726,
%T 93499812718,1329429617150,18902457108916,268763744810865,
%U 3821403968991766,54334437063306418,772551392056456162
%N Number of 3Xn arrays of occupancy after each element moves to some horizontal or antidiagonal neighbor, without move-in move-out left turns
%C Row 3 of A221609
%H R. H. Hardin, <a href="/A221611/b221611.txt">Table of n, a(n) for n = 1..56</a>
%e Some solutions for n=3
%e ..1..2..0....0..3..1....0..3..1....0..2..1....0..2..1....1..1..0....1..2..0
%e ..0..3..1....1..1..0....0..1..0....0..2..2....0..3..1....0..3..1....0..2..1
%e ..0..1..1....1..2..0....2..2..0....0..2..0....1..1..0....1..2..0....1..2..0
%K nonn
%O 1,2
%A _R. H. Hardin_ Jan 20 2013