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

1,3

Links

Table of n, a(n) for n=1..15.

Example

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.

Sequence in context: A195641 A195642 A195643 * A041951 A365362 A143762

Adjacent sequences: A195635 A195636 A195637 * A195639 A195640 A195641

Keyword

nonn

Author

R. H. Hardin, Sep 21 2011

Extensions

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

Status

approved