A180841 Number of nX3 arrays containing 3 indistinguishable copies of 1..n with lexicographical ordering of rows strictly increasing and columns strictly decreasing

1, 1, 19, 596, 37423, 3746117, 545626043, 109162526742, 28754907355070

Offset

1,3

Comments

Column 3 of A180843

Links

Table of n, a(n) for n=1..9.

Example

All solutions for 3X3
..1..1..1....2..1..1....2..1..1....2..1..1....2..1..1....2..1..1....2..1..1
..3..2..2....2..2..1....2..3..1....2..3..1....2..3..1....2..3..2....2..3..2
..3..3..2....3..3..3....2..3..3....3..3..2....3..2..3....3..3..1....3..1..3
...
..2..1..1....2..1..1....2..1..1....2..1..1....2..2..1....2..2..1....2..2..1
..2..3..3....3..2..1....3..2..1....3..2..2....3..1..1....3..1..1....3..1..2
..3..2..1....3..3..2....3..2..3....3..3..1....3..3..2....3..2..3....3..3..1
...
..2..2..1....2..2..1....2..2..1....2..2..2....3..1..1
..3..1..2....3..1..3....3..2..1....3..1..1....3..2..1
..3..1..3....3..2..1....3..3..1....3..3..1....3..2..2

Crossrefs

Sequence in context: A075879 A287936 A226584 * A266052 A317029 A183516

Adjacent sequences: A180838 A180839 A180840 * A180842 A180843 A180844

Keyword

nonn

Author

R. H. Hardin Sep 20 2010

Status

approved