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%I #6 Mar 31 2012 12:35:56
%S 1,3,11,21,61,179,447,1243,3359,9465,25445,70661,201081,558071,
%T 1590047,4493647,12802275,36449535,103943735,298249607,853537659,
%U 2455980115,7066375759,20376225441,58856195841,170131643499,492840266543
%N Number of strings of n+2 numbers x(i) in -1..1 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 1 of A184061
%H R. H. Hardin, <a href="/A184053/b184053.txt">Table of n, a(n) for n = 1..144</a>
%e Some solutions for n=4
%e ..0....0....1...-1....0....0...-1....0....0....0...-1....0...-1....1....0...-1
%e ..0....0....1....0...-1....1....0....1....0...-1....0....1....0....0...-1...-1
%e ..0....1...-1....0....0....0....0....0...-1...-1....0....0...-1....0....0....1
%e ..0....0....0....0...-1....0....1....1....0....1....0....0....1...-1....0....0
%e ..0....0...-1....1....1...-1....0...-1....0....0....0....0....1....0....1....1
%e ..0...-1....0....0....1....0....0...-1....1....1....1...-1....0....0....0....0
%K nonn
%O 1,2
%A _R. H. Hardin_ Jan 09 2011