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 A209031 Number of n-bead necklaces labeled with numbers -7..7 allowing reversal, with sum zero and first differences in -7..7. 1
 1, 4, 12, 88, 625, 5648, 52208, 505857, 4992048, 50169067, 510807173, 5260218485, 54684221779, 573168585795, 6050541798221, 64271927631233, 686512535921878, 7369066749454264, 79449368494683376, 859987831858141180, 9342319735394175920, 101820772577694786504 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Andrew Howroyd, Table of n, a(n) for n = 1..50 EXAMPLE Some solutions for n=6: .-6...-3...-5...-3...-2...-5...-4...-4...-3...-5...-4...-4...-5...-3...-3...-5 .-4...-1...-4...-1...-2...-2....1...-3....0...-3...-1...-1...-5...-1...-2...-2 ..1...-2....2....5....0....2....0....1....1....4....2...-1....1...-1....4...-2 ..4...-1....1...-2....0...-1....2....4...-2...-1....0....4....5....6....4....5 ..6....5....6....0....2....4....0...-1....0....3....1....2....2...-1...-3....3 .-1....2....0....1....2....2....1....3....4....2....2....0....2....0....0....1 CROSSREFS Column 7 of A209032. Sequence in context: A194004 A064280 A203379 * A096424 A009629 A203110 Adjacent sequences:  A209028 A209029 A209030 * A209032 A209033 A209034 KEYWORD nonn AUTHOR R. H. Hardin, Mar 04 2012 EXTENSIONS a(14)-a(22) from Andrew Howroyd, Mar 12 2017 STATUS approved

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Last modified September 25 22:38 EDT 2020. Contains 337346 sequences. (Running on oeis4.)