A188350 Number of arrangements of n+1 numbers x(i) in -1..1 with the sum of x(i)*x(i+1) equal to zero.

5, 15, 29, 91, 197, 627, 1477, 4671, 11693, 36487, 95405, 293695, 792525, 2412175, 6660989, 20097243, 56450693, 169229571, 481426405, 1436666475, 4126292293, 12275100443, 35511918037, 105423983379, 306684489749, 909271908483

Offset: 1

Author

R. H. Hardin Mar 28 2011

Keywords

• nonn

Comments

Column 1 of A188358

Examples

			Some solutions for n=4
..1....0....1...-1....0...-1....1....0....1...-1....0....0...-1...-1...-1....0
..0....0....0....0....0...-1....0....1....1....0....0....0....1....0....0....0
.-1...-1....1....1...-1....1...-1...-1....0...-1...-1...-1....1....0....0....1
.-1....0....0...-1....0....0....0...-1...-1....1....0...-1....0....0...-1....1
..1....1...-1...-1...-1....1...-1....0....1....1....0....1...-1...-1....0...-1
		

Links

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