A215785 Number of permutations of 0..floor((n*7-1)/2) on even squares of an n X 7 array such that each row, column, diagonal and (downwards) antidiagonal of even squares is increasing.

1, 5, 42, 262, 2465, 15485, 146205, 918637, 8674386, 54503318, 514658321, 3233726365, 30535100957, 191859642509, 1811672635826, 11383190276278, 107488026474001, 675374034791837, 6377352953765373, 40070496565665517

Offset

1,2

Comments

Column 7 of A215788.

Links

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

Formula

Empirical: a(n) = 61*a(n-2) - 99*a(n-4) - 2*a(n-6).

Empirical g.f.: x*(1 + 5*x - 19*x^2 - 43*x^3 + 2*x^4 - 2*x^5) / (1 - 61*x^2 + 99*x^4 + 2*x^6). - Colin Barker, Jul 23 2018

Example

Some solutions for n=4:
..0..x..1..x..2..x..3....0..x..1..x..3..x..4....0..x..1..x..2..x..6
..x..4..x..6..x..7..x....x..2..x..5..x..6..x....x..3..x..4..x..8..x
..5..x..8..x..9..x.12....7..x..8..x..9..x.10....5..x..7..x.10..x.12
..x.10..x.11..x.13..x....x.11..x.12..x.13..x....x..9..x.11..x.13..x

Crossrefs

Cf. A215788.

Sequence in context: A266021 A062021 A241780 * A082145 A126765 A228793

Adjacent sequences: A215782 A215783 A215784 * A215786 A215787 A215788

Keyword

nonn

Author

R. H. Hardin, Aug 23 2012

Status

approved