A195638 Number of lower triangles of an n X n 0..n 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, 391, 25532, 5539434, 4116290300, 10699755803977, 98834805799836193, 3285452504354615242708, 397045217438108647483964418, 175907525023476787251523714204914, 287726899459800056272961335544498108972, 1747931723877860528675045077016711589788124993

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
..2.0......0.2......2.0......0.2......2.0......1.1......1.1......2.0
..1.1.1....1.1.1....0.2.1....2.1.0....1.2.0....0.2.1....2.1.0....1.0.2
..0.2.1.1..2.0.1.1..1.1.1.1..1.0.2.1..0.1.2.1..2.0.1.1..0.1.2.1..0.3.0.1
		

Crossrefs

Diagonal of A195644.

Extensions

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