A278721 Number of nX2 0..3 arrays with rows in nondecreasing lexicographic order and columns in nonincreasing lexicographic order.

10, 60, 275, 1050, 3492, 10401, 28288, 71266, 168155, 374868, 795158, 1614184, 3151188, 5939970, 10848924, 19256291, 33301148, 56236656, 92919425, 150477730, 239211960, 373793355, 574842060, 870983100, 1301499381, 1919724600

Offset

1,1

Comments

Column 2 of A278727.

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = (1/479001600)*n^12 + (1/7257600)*n^11 + (1/248832)*n^10 + (103/1451520)*n^9 + (12631/14515200)*n^8 + (2663/345600)*n^7 + (433049/8709120)*n^6 + (342073/1451520)*n^5 + (1269197/1555200)*n^4 + (3605419/1814400)*n^3 + (521131/166320)*n^2 + (997/360)*n + 1

Example

Some solutions for n=4
..2..0. .0..0. .1..0. .1..0. .2..0. .1..0. .1..0. .0..0. .1..0. .0..0
..2..1. .2..1. .1..0. .3..1. .2..1. .2..3. .3..0. .3..1. .1..0. .2..1
..2..1. .2..1. .2..2. .3..1. .3..0. .3..2. .3..2. .3..3. .1..3. .3..1
..3..1. .3..2. .2..3. .3..3. .3..3. .3..3. .3..3. .3..3. .1..3. .3..3

Crossrefs

Cf. A278727.

Sequence in context: A349415 A228581 A241929 * A341366 A004406 A003472

Adjacent sequences: A278718 A278719 A278720 * A278722 A278723 A278724

Keyword

nonn

Author

R. H. Hardin, Nov 27 2016

Status

approved