A221622 Number of nX7 arrays with each row a permutation of 1..7 having at least as many downsteps as the preceding row

5040, 17052210, 49096652080, 130516916069715, 332469512259607296, 827196295133181978340, 2031241364747667201263520, 4951481629224145844957738085, 12021159412525485182456506260880

Offset

1,1

Comments

Column 7 of A221623

Links

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

Formula

Empirical: a(n) = 5040*a(n-1) -8349390*a(n-2) +5234439280*a(n-3) -936232732785*a(n-4) +51206316902496*a(n-5) -99624831647040*a(n-6) +49349521382400*a(n-7)

Example

Some solutions for n=3
..1..4..2..3..5..6..7....1..4..2..3..5..6..7....1..4..2..3..5..6..7
..2..1..3..7..6..4..5....2..1..3..5..4..6..7....2..1..3..6..7..5..4
..3..6..5..7..2..1..4....2..1..3..5..7..4..6....6..2..5..4..3..7..1

Crossrefs

Sequence in context: A063411 A008552 A221437 * A318714 A227669 A010800

Adjacent sequences: A221619 A221620 A221621 * A221623 A221624 A221625

Keyword

nonn

Author

R. H. Hardin Jan 21 2013

Status

approved