A199892 Number of -2..2 arrays x(0..n-1) of n elements with zero sum, and adjacent elements not both strictly positive and not both strictly negative

1, 5, 15, 49, 159, 533, 1783, 6027, 20437, 69665, 238191, 817083, 2809845, 9685397, 33450675, 115736335, 401065951, 1391807783, 4836111471, 16823523661, 58586196339, 204217367081, 712482836479, 2487770630935, 8693076444331

Offset

1,2

Comments

Column 2 of A199898

Links

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

Example

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

Crossrefs

Sequence in context: A077841 A126945 A191641 * A152809 A344204 A034539

Adjacent sequences: A199889 A199890 A199891 * A199893 A199894 A199895

Keyword

nonn

Author

R. H. Hardin Nov 11 2011

Status

approved