A215290 Number of permutations of 0..floor((n*6-1)/2) on even squares of an nX6 array such that each row and column of even squares is increasing.

1, 20, 420, 23100, 1051050, 85765680, 5703417720, 577185873264, 48236247979920, 5595404765670720, 545152292883918720, 69506917342699636800, 7562187114225380722800, 1033498905610802032116000

Offset: 1

Author

R. H. Hardin Aug 07 2012

Keywords

• nonn

Comments

Column 6 of A215292

Examples

			Some solutions for n=4
..0..x..2..x..6..x....1..x..6..x..7..x....1..x..2..x..7..x....0..x..2..x..6..x
..x..1..x..3..x..5....x..0..x..2..x..4....x..0..x..4..x.10....x..3..x..5..x..7
..4..x..9..x.10..x....9..x.10..x.11..x....3..x..6..x..8..x....1..x..9..x.11..x
..x..7..x..8..x.11....x..3..x..5..x..8....x..5..x..9..x.11....x..4..x..8..x.10
		

Links

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

Formula

f3=floor((n+1)/2)

f4=floor(n/2)

a(n) = A060854(3,f3)*A060854(3,f4)*binomial(3*f3+3*f4,3*f3)