A188253 Number of arrangements of 7 nonzero numbers x(i) in -n..n with the sum of x(i)*x(i+1) equal to zero

40, 1284, 12692, 58824, 193232, 521124, 1142180, 2347608, 4323448, 7567844, 12129300, 19691552, 29057776, 42900188, 61593740, 86648240

Offset

1,1

Comments

Row 5 of A188249

Links

Table of n, a(n) for n=1..16.

Example

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

Crossrefs

Sequence in context: A278381 A251202 A239189 * A049396 A135644 A165371

Adjacent sequences: A188250 A188251 A188252 * A188254 A188255 A188256

Keyword

nonn

Author

R. H. Hardin Mar 25 2011

Status

approved