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

1,3

Comments

Column 6 of A195522

Links

Table of n, a(n) for n=1..8.

Example

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

Crossrefs

Sequence in context: A185834 A264249 A195890 * A128897 A201265 A221390

Adjacent sequences: A195517 A195518 A195519 * A195521 A195522 A195523

Keyword

nonn

Author

R. H. Hardin Sep 20 2011

Status

approved