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 A208998 Number of 7-bead necklaces labelled with numbers -n..n not allowing reversal, with sum zero and first differences in -n..n 1
 9, 155, 1111, 4935, 16307, 44209, 104001, 219929, 428031, 779487, 1344353, 2215747, 3514415, 5393753, 8045199, 11704103, 16655941, 23243017, 31871521, 43019059, 57242537, 75186543, 97592047, 125305621, 159288983, 200629037, 250548251 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Row 7 of A208993 LINKS R. H. Hardin, Table of n, a(n) for n = 1..144 FORMULA Empirical: a(n) = a(n-1) +a(n-2) +a(n-3) -a(n-4) -2*a(n-5) -a(n-6) +a(n-8) +a(n-9) +a(n-10) +a(n-12) -a(n-13) -a(n-15) -a(n-16) -a(n-17) +a(n-19) +2*a(n-20) +a(n-21) -a(n-22) -a(n-23) -a(n-24) +a(n-25) EXAMPLE Some solutions for n=6 .-5...-5...-2...-6...-6...-3...-4...-2...-2...-5...-4...-3...-5...-6...-4...-4 ..0....0...-1...-1....0...-2....1....1....2....1...-1...-1...-1...-3...-4...-2 ..3....3....1....2....3....4...-2....0....1....0...-2....0....1....2....1....0 ..0....4....1....3....5...-2....1....0...-1...-2....2....3...-1....2...-1....4 ..1....0...-2....6....3....1....3....0....0....1....0....1....2....1....4....3 ..3....1....2....0...-1....1....0....2....0....5....5....1....4....5....3...-3 .-2...-3....1...-4...-4....1....1...-1....0....0....0...-1....0...-1....1....2 CROSSREFS Sequence in context: A173982 A185759 A215557 * A208545 A183471 A109677 Adjacent sequences:  A208995 A208996 A208997 * A208999 A209000 A209001 KEYWORD nonn AUTHOR R. H. Hardin Mar 04 2012 STATUS approved

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