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%I #6 Mar 31 2012 12:36:37
%S 1,5,15,49,159,533,1783,6027,20437,69665,238191,817083,2809845,
%T 9685397,33450675,115736335,401065951,1391807783,4836111471,
%U 16823523661,58586196339,204217367081,712482836479,2487770630935,8693076444331
%N Number of -2..2 arrays x(0..n-1) of n elements with zero sum, and adjacent elements not both strictly positive and not both strictly negative
%C Column 2 of A199898
%H R. H. Hardin, <a href="/A199892/b199892.txt">Table of n, a(n) for n = 1..200</a>
%e Some solutions for n=6
%e .-2....1...-1...-1...-1....1....1...-2...-1....0....2....0....1....0...-2....0
%e ..0...-1....0....0....2...-1...-1....0....0....1....0...-2....0....2....1....1
%e ..0....0....0...-1...-1....0....1....2....0...-1....0....0...-2...-2...-1...-1
%e ..0....2....0....2....2....0...-2...-1....2....0...-2....2....0....1....2....1
%e ..2...-2....2...-1....0....0....0....1...-2....1....0...-2....1...-1...-1....0
%e ..0....0...-1....1...-2....0....1....0....1...-1....0....2....0....0....1...-1
%K nonn
%O 1,2
%A _R. H. Hardin_ Nov 11 2011
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