login
A278721
Number of nX2 0..3 arrays with rows in nondecreasing lexicographic order and columns in nonincreasing lexicographic order.
1
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
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
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 27 2016
STATUS
approved