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A221624 Number of 2Xn arrays with each row a permutation of 1..n having at least as many downsteps as the preceding row 1
1, 3, 27, 410, 10055, 353654, 17052210, 1075295220, 86037489675, 8510611773950, 1020010974544958, 145633667181394028, 24424236713657975558, 4754016566455947216412, 1062903928921857001102308 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Row 2 of A221623

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..16

EXAMPLE

Some solutions for n=3

..2..3..1....2..3..1....2..1..3....3..1..2....2..1..3....1..3..2....1..2..3

..3..2..1....1..3..2....2..3..1....2..1..3....2..1..3....2..3..1....1..2..3

CROSSREFS

Sequence in context: A201696 A011781 A094577 * A108525 A136719 A279844

Adjacent sequences:  A221621 A221622 A221623 * A221625 A221626 A221627

KEYWORD

nonn

AUTHOR

R. H. Hardin Jan 21 2013

STATUS

approved

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Last modified May 26 13:59 EDT 2022. Contains 354092 sequences. (Running on oeis4.)