A195887 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 <=18

1, 1, 7, 175, 14831, 4857647, 5181491667

Offset

1,3

Comments

Column 3 of A195892

Links

Table of n, a(n) for n=1..7.

Example

Some solutions for n=4
..0........0........0........0........0........0........0........0
.-2.2.....-2.2......0.0.....-1.1......2-2......2-2......0.0.....-2.2
..0.0.0....1-1.0...-1.1.0...-2.1.1....0.0.0...-2.3-1....1-1.0...-1-1.2
..2-2.0.0..1-1.0.0..1-1.0.0..3-2-1.0.-2.2.0.0..0-1.1.0.-1.1.0.0..3-1-2.0

Crossrefs

Sequence in context: A012500 A220326 A094257 * A162082 A195517 A239575

Adjacent sequences: A195884 A195885 A195886 * A195888 A195889 A195890

Keyword

nonn

Author

R. H. Hardin Sep 24 2011

Status

approved