A215867 Number of permutations of 0..floor((n*7-2)/2) on odd squares of an n X 7 array such that each row, column, diagonal and (downwards) antidiagonal of odd squares is increasing.

1, 5, 29, 262, 1642, 15485, 97289, 918637, 5772013, 54503318, 342457898, 3233726365, 20318307913, 191859642509, 1205501906765, 11383190276278, 71523418913482, 675374034791837, 4243543228336841, 40070496565665517

Offset

1,2

Comments

Column 7 of A215870.

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 +32*x^2 +43*x^3 +28*x^4 +2*x^5) / ( 1 -61*x^2 +99*x^4 +2*x^6 ). - R. J. Mathar, Nov 27 2015

Example

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

Crossrefs

Sequence in context: A134752 A370768 A231712 * A342423 A342449 A345098

Adjacent sequences: A215864 A215865 A215866 * A215868 A215869 A215870

Keyword

nonn

Author

R. H. Hardin, Aug 25 2012

Status

approved