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

1,2

Comments

Column 6 of A215788.

Links

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

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

Example

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

Crossrefs

Cf. A215788.

Sequence in context: A326517 A248119 A240764 * A061780 A249411 A156021

Adjacent sequences: A215781 A215782 A215783 * A215785 A215786 A215787

Keyword

nonn

Author

R. H. Hardin, Aug 23 2012

Status

approved