A195639 - OEIS

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

(list; graph; refs; listen; history; text; internal format)

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

..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.

Sequence in context: A229832 A219270 A071381 * A195640 A195641 A195642

Adjacent sequences: A195636 A195637 A195638 * A195640 A195641 A195642

KEYWORD

nonn

AUTHOR

R. H. Hardin, Sep 21 2011

EXTENSIONS

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

STATUS

approved