A188252 Number of arrangements of 6 nonzero numbers x(i) in -n..n with the sum of x(i)*x(i+1) equal to zero

0, 300, 1632, 7092, 16484, 43440, 75080, 142532, 232432, 380244, 525668, 841504, 1099064, 1531092, 2070976, 2785252, 3396316, 4539424, 5414024, 6981628, 8554708, 10387240, 11982424, 15101088, 17498972

Offset

1,2

Comments

Row 4 of A188249

Links

Table of n, a(n) for n=1..25.

Example

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

Crossrefs

Sequence in context: A253650 A054026 A237773 * A128391 A328132 A234412

Adjacent sequences: A188249 A188250 A188251 * A188253 A188254 A188255

Keyword

nonn

Author

R. H. Hardin Mar 25 2011

Status

approved