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%I #5 Mar 31 2012 12:35:56
%S 1,9,31,107,501,2339,10303,44523,198695,888601,3941855,18017983,
%T 83483541,389450325,1838319253,8707491533,41316656737,196349474191,
%U 934444664373,4453775875859,21254863852755,101613183769703,486794625431383
%N Number of strings of n+2 numbers x(i) in -2..2 with the sum of x(i) equal to zero and the sums of x(i)*x(i+1) and x(i)*x(i+2) equal to each other
%C Column 2 of A184061
%H R. H. Hardin, <a href="/A184054/b184054.txt">Table of n, a(n) for n = 1..40</a>
%e Some solutions for n=4
%e ..2...-2....0....2...-2....0....0...-1....2...-1...-1...-1...-2....2....1....2
%e .-2....1....1....0....0...-2...-2....0....1....0....0....2....0....0....1...-1
%e .-1....0....0....0...-2...-2....0....0...-2....0....0....0....0....2...-1....1
%e ..0....2...-2...-2....2....2...-2...-2....1....1....0...-1....0...-2....0....1
%e ..0....1....1....0....2....0....2....2...-1....2....0...-2....2...-2....1...-2
%e ..1...-2....0....0....0....2....2....1...-1...-2....1....2....0....0...-2...-1
%K nonn
%O 1,2
%A _R. H. Hardin_ Jan 09 2011