A215291 Number of permutations of 0..floor((n*7-1)/2) on even squares of an nX7 array such that each row and column of even squares is increasing

1, 35, 2310, 210210, 42882840, 5703417720, 2061378118800, 337653735859440, 173457547735792320, 32436561426593163840, 21174123919831066023840, 4340695403565368534887200, 3373030378241974592216989200

Offset

1,2

Comments

Column 7 of A215292

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(4,f3)*A060854(3,f4)*binomial(4*f3+3*f4,4*f3)

Example

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

Crossrefs

Sequence in context: A001825 A094187 A202921 * A249886 A290584 A174749

Adjacent sequences: A215288 A215289 A215290 * A215292 A215293 A215294

Keyword

nonn

Author

R. H. Hardin Aug 07 2012

Status

approved