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

Author

R. H. Hardin, Nov 27 2016

Keywords

• nonn

Comments

Column 2 of A278727.

Examples

			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
		

Links

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

Crossrefs

Cf. A278727.

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