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%I #9 Mar 19 2017 01:12:16
%S 6,11,20,45,104,290,796,2366,7076,21684,66996,209594,659560,2090590,
%T 6659120,21312716,68476512,220798322,714144612,2316303916,7531662344,
%U 24545750474,80160395804,262280793024,859662037240,2822180991508,9278652591844,30547892144882
%N Number of 2n-bead necklaces labeled with numbers 1..7 not allowing reversal, with neighbors differing by exactly 1.
%H Andrew Howroyd, <a href="/A208726/b208726.txt">Table of n, a(n) for n = 1..100</a>
%e All solutions for n=2:
%e ..5....1....2....3....5....4....2....4....6....1....3
%e ..6....2....3....4....6....5....3....5....7....2....4
%e ..5....1....2....5....7....4....4....6....6....3....3
%e ..6....2....3....4....6....5....3....5....7....2....4
%Y Column 7 of A208727.
%K nonn
%O 1,1
%A _R. H. Hardin_, Mar 01 2012
%E a(13)-a(28) from _Andrew Howroyd_, Mar 18 2017
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