A195518 Number of lower triangles of an n X n -4..4 array with all row and column sums zero.

1, 1, 9, 369, 121367, 286168923, 5151383545261, 720374496860187931, 798423610752730381095001

Offset: 1

Author

R. H. Hardin Sep 20 2011

Keywords

• nonn

Comments

Column 4 of A195522

Examples

			Some solutions for n=4
..0........0........0........0........0........0........0........0
..3-3......4-4......3-3.....-3.3.....-3.3.....-1.1.....-2.2......1-1
.-3.4-1....0.0.0...-3.0.3....2-1-1....2-3.1....0-4.4...-2.1.1....1.0-1
..0-1.1.0.-4.4.0.0..0.3-3.0..1-2.1.0..1.0-1.0..1.3-4.0..4-3-1.0.-2.1.1.0