A221625 Number of 3Xn arrays with each row a permutation of 1..n having at least as many downsteps as the preceding row.

1, 4, 112, 6120, 738150, 148700748, 49096652080, 24099422236160, 17023170538890750, 16517958827528755300, 21433818529290626472948, 36180795747764068402865136, 77856103174007703918070147632

Offset: 1

Author

R. H. Hardin Jan 21 2013

Keywords

• nonn

Comments

Row 3 of A221623

Examples

			Some solutions for n=3
..3..1..2....1..2..3....1..3..2....1..2..3....1..2..3....2..3..1....2..3..1
..1..3..2....3..1..2....3..1..2....1..2..3....2..1..3....2..3..1....1..3..2
..1..3..2....2..3..1....3..2..1....1..2..3....3..2..1....2..1..3....3..1..2
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..14