A188250 Number of arrangements of 4 nonzero numbers x(i) in -n..n with the sum of x(i)*x(i+1) equal to zero

0, 20, 52, 144, 208, 436, 532, 816, 1072, 1508, 1668, 2400, 2592, 3220, 3940, 4768, 5024, 6212, 6500, 7856, 8944, 9988, 10340, 12384, 13280, 14516, 15796, 17824, 18272, 21156, 21636, 23712, 25472, 27124, 29124, 32800, 33376, 35220, 37300, 41136, 41776

Offset

1,2

Comments

Row 2 of A188249

Links

R. H. Hardin, Table of n, a(n) for n = 1..135

Example

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

Crossrefs

Sequence in context: A183047 A209982 A205220 * A329627 A329628 A302885

Adjacent sequences: A188247 A188248 A188249 * A188251 A188252 A188253

Keyword

nonn

Author

R. H. Hardin Mar 25 2011

Status

approved