A199897 Number of -7..7 arrays x(0..n-1) of n elements with zero sum, and adjacent elements not both strictly positive and not both strictly negative

1, 15, 85, 799, 5839, 51395, 406575, 3500269, 28684325, 245319361, 2048301005, 17499467353, 147731409251, 1263413909311, 10741266363733, 92019265611439, 786112365529335, 6747253002120179, 57843127733658007, 497375672047480891

Offset

1,2

Comments

Column 7 of A199898

Links

R. H. Hardin, Table of n, a(n) for n = 1..200

Example

Some solutions for n=6
..1....3....2...-6...-4...-2...-7....2...-7....2....5...-6...-3....6....5....0
..0...-4...-5....7....7....0....6...-4....1....0....0....1....0...-2....0....6
.-1....0....6...-4....0....0....0....7...-3....1...-1...-3....0....2...-7...-5
..2....0...-7....2...-1....4...-6...-3....6...-7....0....4....7...-1....2....0
.-3...-2....7...-2....5...-5....0....1...-4....5....2...-3...-7....0...-3...-1
..1....3...-3....3...-7....3....7...-3....7...-1...-6....7....3...-5....3....0

Crossrefs

Sequence in context: A138322 A206170 A177882 * A367228 A309922 A302948

Adjacent sequences: A199894 A199895 A199896 * A199898 A199899 A199900

Keyword

nonn

Author

R. H. Hardin Nov 11 2011

Status

approved