A215784 Number of permutations of 0..floor((n*6-1)/2) on even squares of an n X 6 array such that each row, column, diagonal and (downwards) antidiagonal of even squares is increasing.

1, 2, 12, 29, 189, 458, 2988, 7241, 47241, 114482, 746892, 1809989, 11808549, 28616378, 186696108, 452432081, 2951712081, 7153064162, 46667304972, 113091730349, 737821743309, 1788008493098, 11665145978028, 28268860698521

Offset: 1

Author

R. H. Hardin, Aug 23 2012

Keywords

• nonn

Comments

Column 6 of A215788.

Examples

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

Links

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

Crossrefs

Cf. A215788.

Formula

Empirical: a(n) = 16*a(n-2) - 3*a(n-4).

Empirical g.f.: x*(1 + 3*x)*(1 - x - x^2) / (1 - 16*x^2 + 3*x^4). - Colin Barker, Jul 23 2018