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%I #6 Mar 31 2012 12:36:11
%S 16,20,120,300,1284,4132,16272,57808,223308,828456,3193588,12106616,
%T 46777036,179484068,695670728,2689241588,10454975104,40616587968,
%U 158328346172,617266507080,2411727117520,9427476168776,36906793159556
%N Number of arrangements of n+2 nonzero numbers x(i) in -2..2 with the sum of x(i)*x(i+1) equal to zero
%C Column 2 of A188249
%H R. H. Hardin, <a href="/A188242/b188242.txt">Table of n, a(n) for n = 1..200</a>
%e Some solutions for n=4
%e .-2...-1...-1....2....2...-1....1...-1...-2....1....1...-1....1...-1....2...-2
%e ..2....2...-1....1....1....2...-1....2....2...-2...-1....1....1....2....2....1
%e ..1....1....1...-1....1....1....1....2....1...-1...-1....1...-2...-2...-1....2
%e .-1....1....2....1...-2...-2....2...-1....2....2...-2...-1...-2...-2....2...-1
%e .-1....1...-2....2....1...-2...-1...-2....2....2....2....1....1...-2....1....2
%e .-2...-2...-1...-1....1....1...-2....1...-2...-1....1....2...-1....1...-2....2
%K nonn
%O 1,1
%A _R. H. Hardin_ Mar 25 2011
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