A180837 Number of nX3 arrays containing 3 indistinguishable copies of 1..n with rows and columns in lexicographically strictly increasing order

1, 1, 77, 5385, 545426, 79230924, 15755497776, 4122239926855

Offset

1,3

Comments

Column 3 of A180839

Links

Table of n, a(n) for n=1..8.

Example

Some solutions for 3X3
..1..1..2....1..1..2....1..1..2....1..1..2....1..1..2....1..1..2....1..1..2
..1..2..3....1..2..2....1..2..3....1..2..3....1..3..2....1..3..3....1..3..3
..2..3..3....3..3..3....3..3..2....3..2..3....2..3..3....2..3..2....2..2..3
...
..1..1..2....1..1..2....1..1..2....1..1..3....1..1..3....1..1..3....1..1..3
..1..3..2....1..3..2....1..3..3....1..2..2....1..2..3....1..2..3....1..2..2
..3..3..2....3..2..3....3..2..2....2..3..3....2..3..2....2..2..3....3..3..2
...
..1..1..3....1..1..3....1..1..3....1..1..3....1..1..3....1..1..3....1..1..1
..1..2..2....1..2..3....1..3..2....1..3..2....1..3..3....1..3..2....2..2..3
..3..2..3....3..2..2....2..3..2....2..2..3....2..2..2....3..2..2....2..3..3
...
..1..1..2....1..1..2....1..1..2....1..1..2....1..1..2....1..1..2....1..1..2
..2..3..1....2..3..1....2..3..1....2..3..2....2..3..2....2..3..3....2..3..3
..2..3..3....3..3..2....3..2..3....3..3..1....3..1..3....3..1..2....3..2..1

Crossrefs

Sequence in context: A217455 A116319 A217962 * A361112 A210811 A107787

Adjacent sequences: A180834 A180835 A180836 * A180838 A180839 A180840

Keyword

nonn

Author

R. H. Hardin Sep 20 2010

Status

approved