A215289 Number of permutations of 0..floor((n*5-1)/2) on even squares of an nX5 array such that each row and column of even squares is increasing

1, 10, 140, 2100, 60060, 1051050, 42882840, 814773960, 41227562376, 824551247520, 48236247979920, 999179422441200, 64899082486180800, 1379105502831342000, 96951116849043342600, 2100607531729272423000, 157112712418611824074200

Offset

1,2

Comments

Column 5 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(3,f3)*A060854(2,f4)*binomial(3*f3+2*f4,3*f3)

Example

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

Crossrefs

Sequence in context: A089834 A132505 A254336 * A319578 A051618 A295034

Adjacent sequences: A215286 A215287 A215288 * A215290 A215291 A215292

Keyword

nonn

Author

R. H. Hardin Aug 07 2012

Status

approved