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%I #5 Mar 31 2012 12:35:55
%S 1,1,5,15,81,237,1015,3891,16171,66237,297003,1304467,5981617,
%T 27407859,126441771,584452845,2721978059,12719931479,59862174023,
%U 282898499059,1341705275365,6380905008633,30422523202843,145340620435425
%N Number of strings of n numbers x(i) in -2..2 with sums of x(i) and of x(i)*x(i+1) both zero
%C Column 2 of A183944
%H R. H. Hardin, <a href="/A183937/b183937.txt">Table of n, a(n) for n = 1..81</a>
%e All solutions for n=4
%e ..1....0...-1....1....0...-2....0....1....2....2...-1....0....0...-1...-2
%e ..0...-1....0....2...-2....0....0....0....0....0....0....2....1...-2....0
%e ..0....0....0...-2....0....0....0...-1....0...-2....1....0....0....2....2
%e .-1....1....1...-1....2....2....0....0...-2....0....0...-2...-1....1....0
%K nonn
%O 1,3
%A _R. H. Hardin_ Jan 08 2011
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