%I #12 Oct 03 2025 08:18:10

%S 1,6,32,168,892,4964,27854,156920,891684,5095360,29236016,168361392,

%T 972601784,5633548460,32706291872,190266981972,1108856802378,

%U 6472638961608,37836350087956,221461180199752,1297757839607606

%N Number of -3..3 arrays x(0..n-1) of n elements with zero sum and no two neighbors equal.

%C Column 3 of A199704

%H R. H. Hardin, <a href="/A199699/b199699.txt">Table of n, a(n) for n = 1..200</a>

%e Some solutions for n=5

%e ..1....0....2...-3....1...-3...-2...-3...-2....0....1....2....2....2...-2....0

%e .-1....1....0....1....2....2....1....3...-1....2....2....0....0...-2...-3....3

%e .-3...-1....1...-2...-2....1...-2....0....0....1...-3...-1...-3....3....3....2

%e ..3...-2...-3....1....0...-2....2....1....3...-2....1....1...-1...-1....2...-3

%e ..0....2....0....3...-1....2....1...-1....0...-1...-1...-2....2...-2....0...-2

%K nonn

%O 1,2

%A _R. H. Hardin_, Nov 09 2011