A195885 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 <=2

1, 1, 3, 15, 83, 591, 5281, 56249, 704129, 10236185, 170423795, 3211956071, 67925755107, 1599937402631

Offset

1,3

Comments

Column 1 of A195892

Links

Table of n, a(n) for n=1..14.

Example

Some solutions for n=4
..0........0........0........0........0........0........0........0
..0.0.....-1.1.....-1.1......0.0.....-1.1......0.0......1-1......1-1
..0.0.0....0.0.0....0.0.0...-1.1.0....0.0.0....0-1.1...-1.1.0....0.0.0
..0.0.0.0..1-1.0.0..1-1.0.0..1-1.0.0..1-1.0.0..0.1-1.0..0.0.0.0.-1.1.0.0

Crossrefs

Sequence in context: A118356 A074552 A193658 * A115910 A355094 A106569

Adjacent sequences: A195882 A195883 A195884 * A195886 A195887 A195888

Keyword

nonn

Author

R. H. Hardin Sep 24 2011

Status

approved