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%I #5 Mar 31 2012 12:36:37
%S 1,9,37,209,1043,5725,30199,164993,890299,4877477,26632013,146499083,
%T 805700567,4449304857,24590147861,136249639279,755738351775,
%U 4199211521573,23357174342185,130088542750275,725223072283995
%N Number of -4..4 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 4 of A199898
%H R. H. Hardin, <a href="/A199894/b199894.txt">Table of n, a(n) for n = 1..200</a>
%e Some solutions for n=6
%e .-2....1....0...-2....3....3....1....3...-2....0....3...-1....1....2....4....1
%e ..3....0....4....0....0...-3...-1....0....2...-2....0....0...-1...-3...-2...-1
%e ..0....0...-4....0...-2....0....1...-4...-1....0....0...-1....4....3....1....4
%e ..1...-4....3....0....1...-3...-2....2....0....2....0....2...-2....0...-2....0
%e .-2....0...-3...-2...-2....3....2...-4....1....0....1...-4....2....2....2...-4
%e ..0....3....0....4....0....0...-1....3....0....0...-4....4...-4...-4...-3....0
%K nonn
%O 1,2
%A _R. H. Hardin_ Nov 11 2011