A188255 Number of arrangements of 9 nonzero numbers x(i) in -n..n with the sum of x(i)*x(i+1) equal to zero

140, 16272, 355396, 2880240, 14715004, 55994544, 168083116, 445304272, 1033172284, 2215496776, 4323822892

Offset

1,1

Comments

Row 7 of A188249

Links

Table of n, a(n) for n=1..11.

Example

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

Crossrefs

Sequence in context: A035820 A075915 A159362 * A159366 A189505 A190078

Adjacent sequences: A188252 A188253 A188254 * A188256 A188257 A188258

Keyword

nonn

Author

R. H. Hardin Mar 25 2011

Status

approved