A188247 Number of arrangements of n+2 nonzero numbers x(i) in -7..7 with the sum of x(i)*x(i+1) equal to zero.

196, 532, 10564, 75080, 1142180, 11953848, 168083116, 2026547348, 27843005992, 355600251460, 4851985495460, 63719148177636, 867980001700376, 11577646834184824, 157763834094118596

Offset

1,1

Comments

Column 7 of A188249

Links

Table of n, a(n) for n=1..15.

Example

Some solutions for n=4
.-3...-1...-3....2....4...-6....5....3...-4....2...-1....4...-6...-6....3...-6
.-7...-7...-1...-1...-1...-1...-1....6...-5...-5....1....3...-6....3...-1...-4
..1....2...-6...-2....2...-6....1...-1....3....6...-2...-6....3....2...-2....3
..4....6...-2....3....5....1....4...-6...-3....2....2...-5...-6....6....4...-2
.-2....5....3....3....2....2...-2....2....2....7....7....3...-7....1....3...-6
..5...-7...-5...-1...-7...-4...-5...-3....5....2...-1...-3....6...-6...-1....3

Crossrefs

Sequence in context: A119667 A023108 A092231 * A211851 A089493 A088753

Adjacent sequences: A188244 A188245 A188246 * A188248 A188249 A188250

Keyword

nonn

Author

R. H. Hardin, Mar 25 2011

Status

approved