A188362 Number of arrangements of 7 numbers x(i) in -n..n with the sum of x(i)*x(i+1) equal to zero.

627, 9153, 49747, 181449, 480363, 1171345, 2295051, 4409889, 7651651, 12818961, 19584123, 30982585, 44149827, 63627969, 89493523, 123568713

Offset: 1

Author

R. H. Hardin Mar 28 2011

Keywords

• nonn

Comments

Row 6 of A188358

Examples

			Some solutions for n=4
..0....4....0...-1....0....1...-1...-1....0....2....3....0....1...-1....1...-3
..0...-1....0....0....0...-1...-1...-2...-2....0...-2...-3...-2...-1...-2...-4
.-2....4....0...-1....3...-1....1....1....0...-2....1....2....1...-2...-2....4
.-3...-1....4...-3....1....0....3...-4....4....1....0....1....4....1....3....0
..2....0....0....1...-3....3...-1...-1....1....0....1....0...-2...-1....2...-1
..0....3....0....2....0....0....0....1....2...-2....2...-1...-2....0....2....2
..4....4...-2...-1....3....4...-3....1...-3...-1....3...-4...-2...-3...-3....3