Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #10 Mar 13 2017 05:18:40
%S 1,1,1,1,1,2,2,4,4,7,7,14,16,32,46,90,140,258,416,746,1245,2228,3845,
%T 6929,12194,21990,39113,70544,126293,228168,410887,744377,1346837,
%U 2446229,4441502,8084433,14717678,26841848,48977823,89494630,163634188,299532409
%N Number of n-bead necklaces labeled with numbers -1..1 allowing reversal, with sum zero and first and second differences in -1..1.
%H Andrew Howroyd, <a href="/A208963/b208963.txt">Table of n, a(n) for n = 1..100</a>
%e All solutions for n=8:
%e .-1...-1....0...-1
%e .-1...-1....0...-1
%e ..0....0....0...-1
%e ..0....0....0....0
%e ..1....0....0....1
%e ..1....1....0....1
%e ..0....1....0....1
%e ..0....0....0....0
%Y Column 1 of A208970.
%K nonn
%O 1,6
%A _R. H. Hardin_, Mar 03 2012
%E a(34)-a(42) from _Andrew Howroyd_, Mar 12 2017