A195639 Number of lower triangles of an n X n 0..3 array with all row sums equal to the length of the row and all column sums equal to the length of the column.

1, 1, 3, 19, 379, 22506, 4063437, 2303397986, 4165684145897, 24351094470461293, 465231630106636264261, 29310412705455253400706632, 6135104108066245513806738233622, 4293669524764808720927311131475805624, 10102086274414407316013385512463577654333437

Offset: 1

Author

R. H. Hardin, Sep 21 2011

Keywords

• nonn

Examples

			Some solutions for n=4:
..1........1........1........1........1........1........1........1
..0.2......0.2......1.1......2.0......2.0......0.2......0.2......1.1
..0.1.2....3.0.0....2.0.1....1.2.0....1.0.2....2.1.0....3.0.0....2.0.1
..3.0.0.1..0.1.2.1..0.2.1.1..0.1.2.1..0.3.0.1..1.0.2.1..0.1.2.1..0.2.1.1
		

Crossrefs

Column 3 of A195644.

Extensions

a(12)-a(15) from Andrew Howroyd, May 16 2020