A188351 Number of arrangements of n+1 numbers x(i) in -2..2 with the sum of x(i)*x(i+1) equal to zero.

9, 45, 117, 565, 1953, 9153, 37269, 173409, 766869, 3589357, 16545861, 78195505, 368573829, 1757922765, 8394885777, 40340645213, 194259462205, 938930726781, 4547344031581, 22077243778089, 107366485176765, 523060579628697

Offset: 1

Author

R. H. Hardin Mar 28 2011

Keywords

• nonn

Comments

Column 2 of A188358

Examples

			Some solutions for n=4
..2...-1....1...-1...-2...-1....0....0....0...-1...-1....2....0...-2....1...-1
..0...-2....2....2....1....1...-1....0...-2...-2...-1....0....0....2....2....1
..0....1...-2...-1....0....1....0....0....0...-2...-2...-2....2....1....0....1
..2....0...-2...-2...-2....2....1...-1...-2....2....1....1....0....1...-1....0
..0...-1....1...-1...-1...-1....0....0....0...-1...-1....2....0....1....2...-1
		

Links

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