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%I #8 Dec 30 2012 04:01:50
%S 1,4,14,52,200,708,2642,10000,37984,144876,554120,2128672,8204180,
%T 31697564,122734614,476170124,1850664202,7204005752,28081918548,
%U 109604285492,428278469018,1675246478864,6559126501510,25703606447364
%N Number of -2..2 arrays x(0..n-1) of n elements with zero sum and no two neighbors equal
%C Column 2 of A199704
%H R. H. Hardin, <a href="/A199698/b199698.txt">Table of n, a(n) for n = 1..200</a>
%e Some solutions for n=5
%e ..0....1...-2....0....2...-1....2....2....1....2...-1....2....1....0....2....0
%e .-1....0....2....1...-2....1....1....0...-1...-2....1...-1....2...-1...-1...-1
%e ..1...-1...-1...-2....1...-1...-1...-1....0....0....0....1...-2....1....1....2
%e .-1...-2....0....0...-1....1...-2....1...-2...-1...-1....0...-1....2...-2...-1
%e ..1....2....1....1....0....0....0...-2....2....1....1...-2....0...-2....0....0
%K nonn
%O 1,2
%A _R. H. Hardin_ Nov 09 2011