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A215288 Number of permutations of 0..floor((n*4-1)/2) on even squares of an nX4 array such that each row and column of even squares is increasing 2
1, 6, 30, 280, 2100, 23100, 210210, 2522520, 25729704, 325909584, 3585005424, 47117214144, 546896235600, 7383099180600, 89212448432250, 1229149289511000, 15323394475903800, 214527522662653200, 2742051789669912720 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 4 of A215292

LINKS

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

FORMULA

f3=floor((n+1)/2)

f4=floor(n/2)

a(n) = A060854(2,f3)*A060854(2,f4)*binomial(2*f3+2*f4,2*f3)

EXAMPLE

Some solutions for n=5

..2..x..4..x....0..x..3..x....2..x..3..x....0..x..5..x....1..x..4..x

..x..0..x..1....x..2..x..5....x..0..x..4....x..1..x..3....x..0..x..6

..3..x..7..x....1..x..6..x....5..x..6..x....6..x..7..x....2..x..5..x

..x..6..x..9....x..4..x..7....x..1..x..8....x..2..x..4....x..3..x..8

..5..x..8..x....8..x..9..x....7..x..9..x....8..x..9..x....7..x..9..x

CROSSREFS

Sequence in context: A099031 A066108 A205339 * A295611 A264641 A110374

Adjacent sequences:  A215285 A215286 A215287 * A215289 A215290 A215291

KEYWORD

nonn

AUTHOR

R. H. Hardin Aug 07 2012

STATUS

approved

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Last modified October 22 04:25 EDT 2019. Contains 328315 sequences. (Running on oeis4.)