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%I #5 Mar 31 2012 12:36:45
%S 1,3,15,45,169,643,2509,10129,41031,166337,678169,2772981,11365437,
%T 46717997,192513137,795049313,3289962901,13637608037,56617168555,
%U 235369429109,979676940333,4082222870535,17027439214453,71089263424863
%N Number of zero-sum -3..3 arrays of n elements with first and second differences also in -3..3
%C Column 3 of A201873
%H R. H. Hardin, <a href="/A201868/b201868.txt">Table of n, a(n) for n = 1..210</a>
%e Some solutions for n=9
%e .-3...-3...-1...-1....3...-2...-3...-3....1...-1...-2....3....1...-3...-1...-2
%e ..0....0...-1...-1....2...-1...-1....0....1...-2...-1....1...-1...-1....1....0
%e ..1....1....0....0...-1....1...-2....1....1....0...-2....0....0....0....1....1
%e ..1...-1....2....2...-2....2....0....1....0....0...-1....0...-1....0....0....2
%e ..1...-1....1....1...-2....3....0....3....0....1....0...-3....1...-1...-2....0
%e .-1....1...-1....1....0....1....1....2...-1....2....0...-3....0....1...-1....0
%e .-1....2...-1....0...-1...-2....2....0....0....1....0....0...-1....2....0....1
%e ..0....2...-1...-1...-1...-2....1...-2...-1....0....3....0....1....2....0....0
%e ..2...-1....2...-1....2....0....2...-2...-1...-1....3....2....0....0....2...-2
%K nonn
%O 1,2
%A _R. H. Hardin_ Dec 06 2011
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