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%I #5 Mar 31 2012 12:36:37
%S 1,4,24,72,256,1312,5206,21208,97668,422052,1819620,8158144,36110122,
%T 159422584,712790438,3182921756,14206099012,63688577860,285783359204,
%U 1282956672032,5770687400200,25983122754016,117074268243396
%N Number of -3..3 arrays x(0..n-1) of n elements with zero sum, and adjacent elements not equal modulo three (with -1 modulo 3 = 2)
%C Column 3 of A199909
%H R. H. Hardin, <a href="/A199904/b199904.txt">Table of n, a(n) for n = 1..200</a>
%e Some solutions for n=6
%e .-2....2...-1...-1....1...-2...-1...-2...-3...-3....2....2....2....3...-3...-1
%e ..3...-3....1....0...-3...-1....1....2....2...-1....0....1...-3...-1....2...-2
%e .-2....1....2...-2....1....0...-1....1....1....3....2...-1....1...-3...-3...-3
%e ..2....3....3....0....3....2....0...-3....0...-1...-3...-3...-3...-2....1....2
%e .-3...-2...-2....1...-2....1....1....2...-2....0...-1....1....1....2....2....3
%e ..2...-1...-3....2....0....0....0....0....2....2....0....0....2....1....1....1
%K nonn
%O 1,2
%A _R. H. Hardin_ Nov 11 2011
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