A195521 Number of lower triangles of an n X n -7..7 array with all row and column sums zero

1, 1, 15, 1695, 2563933, 46387885537, 10665939121760907, 31749804821289929290261

Offset

1,3

Comments

Column 7 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
.-1.1......2-2.....-4.4......7-7.....-2.2.....-3.3......3-3......6-6
..3-1-2....1.4-5....3-5.2...-4.0.4...-4.1.3....3-3.0....2.1-3...-2.5-3
.-2.0.2.0.-3-2.5.0..1.1-2.0.-3.7-4.0..6-3-3.0..0.0.0.0.-5.2.3.0.-4.1.3.0

Crossrefs

Sequence in context: A263600 A208860 A195891 * A122184 A069450 A205346

Adjacent sequences: A195518 A195519 A195520 * A195522 A195523 A195524

Keyword

nonn

Author

R. H. Hardin Sep 20 2011

Status

approved