%I #9 Mar 18 2018 18:31:59
%S 2,15,87,371,1185,3186,7425,15658,30368,55222,95087,156612,248194,
%T 380753,567639,825586,1174510,1638724,2246594,3032025,4033918,5298001,
%U 6876080,8828154,11221516,14133153,17648642,21864897,26888831,32840460,39851308
%N Number of 7-bead necklaces labeled with numbers -n..n allowing reversal, with sum zero and first and second differences in -n..n.
%C Row 7 of A208970.
%H R. H. Hardin, <a href="/A208974/b208974.txt">Table of n, a(n) for n = 1..79</a>
%e Some solutions for n=5:
%e -5 -4 -3 -3 -1 -4 -3 -1 -4 -3 -3 -4 -4 -3 -2 -1
%e -3 -3 -3 -1 -1 -2 -3 -1 -2 -3 -2 -3 -4 -3 -1 0
%e 0 1 0 -3 0 0 0 -1 3 0 2 -1 0 1 -1 0
%e 3 2 -1 0 -1 1 0 -1 3 0 2 3 1 1 -1 0
%e 5 2 3 3 1 4 3 -1 0 2 2 4 3 1 3 -1
%e 2 2 3 4 1 2 3 2 1 3 0 3 4 2 3 0
%e -2 0 1 0 1 -1 0 3 -1 1 -1 -2 0 1 -1 2
%K nonn
%O 1,1
%A _R. H. Hardin_, Mar 03 2012