A195520 Number of lower triangles of an n X n -6..6 array with all row and column sums zero.

1, 1, 13, 1105, 1089411, 11131321791, 1252997799222737, 1582560262323178069903

Offset: 1

Author

R. H. Hardin Sep 20 2011

Keywords

• nonn

Comments

Column 6 of A195522

Examples

			Some solutions for n=4
..0........0........0........0........0........0........0........0
..0.0......0.0......0.0.....-3.3.....-5.5.....-2.2......5-5.....-5.5
..4.0-4...-4.4.0....3-2-1...-3.3.0...-1-3.4....4.0-4...-6.4.2....3-4.1
.-4.0.4.0..4-4.0.0.-3.2.1.0..6-6.0.0..6-2-4.0.-2-2.4.0..1.1-2.0..2-1-1.0