A188352 Number of arrangements of n+1 numbers x(i) in -3..3 with the sum of x(i)*x(i+1) equal to zero.

13, 91, 257, 1775, 7369, 49747, 262925, 1763151, 10536621, 70819767, 449413269, 3032790187, 19849674769, 134432007295, 895147297233, 6080318813363, 40910518802585, 278583012405979, 1887082800975125, 12878423767271251

Offset

1,1

Comments

Column 3 of A188358

Links

R. H. Hardin, Table of n, a(n) for n = 1..124

Example

Some solutions for n=4
.-1....2...-2...-1...-3....2....0...-3....0....1....2....3....1....2....1....0
..0...-3....0....0....2...-2....0....1....0....3...-2...-1...-3....0....3....0
..3....0...-1...-2...-2...-2....3....2....2...-1...-2....1...-1....3....0...-2
..0....2....0...-2...-2....0....1....1...-1....0...-3...-2....0....0....1...-3
..0....3....1....2...-3...-3...-3...-1...-2....0....2...-3....2...-1...-3....2

Crossrefs

Sequence in context: A156947 A139613 A212956 * A162631 A247611 A008505

Adjacent sequences: A188349 A188350 A188351 * A188353 A188354 A188355

Keyword

nonn

Author

R. H. Hardin, Mar 28 2011

Status

approved