A195886 Number of lower triangles of an n X n integer array with all row and column sums zero and all row and column sums of squares <=8

1, 1, 5, 65, 1349, 90013, 17612909, 7690681987, 6760358933241

Offset

1,3

Comments

Column 2 of A195892

Links

Table of n, a(n) for n=1..9.

Example

Some solutions for n=4
..0........0........0........0........0........0........0........0
..2-2......2-2.....-1.1......2-2.....-2.2......2-2......2-2.....-2.2
.-2.2.0...-1.2-1....1-1.0...-2.1.1....0-2.2....0.0.0....0.0.0....0.0.0
..0.0.0.0.-1.0.1.0..0.0.0.0..0.1-1.0..2.0-2.0.-2.2.0.0.-2.2.0.0..2-2.0.0

Crossrefs

Sequence in context: A121822 A056245 A357338 * A079482 A147625 A157097

Adjacent sequences: A195883 A195884 A195885 * A195887 A195888 A195889

Keyword

nonn

Author

R. H. Hardin Sep 24 2011

Status

approved