A215295 Number of permutations of 0..floor((n*5-2)/2) on odd squares of an nX5 array such that each row and column of odd squares is increasing

1, 10, 70, 2100, 23100, 1051050, 14294280, 814773960, 12547518984, 824551247520, 13781785137120, 999179422441200, 17699749768958400, 1379105502831342000, 25513451802379827000, 2100607531729272423000, 40191624107086745693400

Offset

1,2

Comments

Column 5 of A215297

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(2,f3)*A060854(3,f4)*binomial(2*f3+3*f4,2*f3)

Example

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

Crossrefs

Sequence in context: A038779 A246427 A172499 * A136856 A016218 A026772

Adjacent sequences: A215292 A215293 A215294 * A215296 A215297 A215298

Keyword

nonn

Author

R. H. Hardin Aug 07 2012

Status

approved