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

1,2

Comments

Row 3 of A221623

Links

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

Example

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

Crossrefs

Sequence in context: A158450 A063406 A361543 * A013151 A006718 A185320

Adjacent sequences: A221622 A221623 A221624 * A221626 A221627 A221628

Keyword

nonn

Author

R. H. Hardin Jan 21 2013

Status

approved