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

Author

R. H. Hardin Jan 21 2013

Keywords

• nonn

Comments

Column 7 of A221623

Examples

			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
		

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) [phone]*a(n-3) -936232732785*a(n-4) [phone]*a(n-5) -99624831647040*a(n-6) [phone]*a(n-7)