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Number of -6..6 arrays x(0..n-1) of n elements with zero sum, and adjacent elements not equal modulo three (with -1 modulo 3 = 2)
1

%I #5 Mar 31 2012 12:36:37

%S 1,8,84,448,3196,29864,216530,1699268,14546928,116482068,950119628,

%T 7969545520,65812921362,546169532636,4575686136942,38231452993064,

%U 320077674218718,2689588505089064,22606933344228744,190257872374203952

%N Number of -6..6 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 6 of A199909

%H R. H. Hardin, <a href="/A199907/b199907.txt">Table of n, a(n) for n = 1..200</a>

%e Some solutions for n=6

%e .-6...-3...-2....0...-5....2....6...-4...-3....0....4....2...-3....2...-5....4

%e ..2...-1....2...-1....5....4...-2....4...-2....1...-4....1...-4...-5...-4...-4

%e ..1....6....0...-5....0...-1...-4...-6....5...-3....0...-3....4...-6....6....3

%e ..5....1....1....5...-5...-6...-2...-2....1...-2....2....5....0....1....4...-2

%e .-2...-1...-4...-3....5...-5....3....5...-1....6....1...-5...-2....5...-4....2

%e ..0...-2....3....4....0....6...-1....3....0...-2...-3....0....5....3....3...-3

%K nonn

%O 1,2

%A _R. H. Hardin_ Nov 11 2011