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

Author

R. H. Hardin Nov 11 2011

Keywords

• nonn

Comments

Column 3 of A199898

Examples

			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
		

Links

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