%I #7 Mar 13 2017 00:02:04

%S 1,2,2,5,8,19,39,95,223,554,1373,3493,8906,23016,59805,156588,412082,

%T 1090443,2897828,7733433,20712345,55661171,150031505,405533996,

%U 1098949141,2985066757,8125987470,22165517960,60575472281,165835969094

%N Number of n-bead necklaces labeled with numbers -1..1 not allowing reversal, with sum zero and avoiding the pattern z z+1 z+2.

%C Column 1 of A209073.

%H R. H. Hardin, <a href="/A209066/b209066.txt">Table of n, a(n) for n = 1..33</a>

%e Some solutions for n=6:

%e .-1...-1...-1...-1....0...-1...-1...-1...-1...-1...-1...-1...-1...-1...-1...-1

%e ..1....0...-1...-1....0...-1....0....1....0...-1....1....0....1....0...-1....0

%e ..0...-1....1....1....0....0....0...-1...-1....1....0....0...-1....0....1....0

%e .-1....1....0...-1....0....0....1....1....1....0....0....0....1....1....1...-1

%e ..1....0....0....1....0....1...-1...-1....1....1....0....1....0....0...-1....1

%e ..0....1....1....1....0....1....1....1....0....0....0....0....0....0....1....1

%K nonn

%O 1,2

%A _R. H. Hardin_, Mar 04 2012