A199893 Number of -3..3 arrays x(0..n-1) of n elements with zero sum, and adjacent elements not both strictly positive and not both strictly negative

1, 7, 25, 111, 461, 2035, 8823, 39053, 172355, 767425, 3420017, 15311495, 68665323, 308805403, 1391091909, 6278869703, 28381760049, 128482271031, 582346682067, 2642616002605, 12004291295381, 54583533395613, 248409301882015

Offset

1,2

Comments

Column 3 of A199898

Links

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

Example

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

Crossrefs

Sequence in context: A327627 A110240 A266810 * A129791 A216688 A141626

Adjacent sequences: A199890 A199891 A199892 * A199894 A199895 A199896

Keyword

nonn

Author

R. H. Hardin Nov 11 2011

Status

approved