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A215290 Number of permutations of 0..floor((n*6-1)/2) on even squares of an nX6 array such that each row and column of even squares is increasing 2
1, 20, 420, 23100, 1051050, 85765680, 5703417720, 577185873264, 48236247979920, 5595404765670720, 545152292883918720, 69506917342699636800, 7562187114225380722800, 1033498905610802032116000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 6 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(3,f3)*A060854(3,f4)*binomial(3*f3+3*f4,3*f3)

EXAMPLE

Some solutions for n=4

..0..x..2..x..6..x....1..x..6..x..7..x....1..x..2..x..7..x....0..x..2..x..6..x

..x..1..x..3..x..5....x..0..x..2..x..4....x..0..x..4..x.10....x..3..x..5..x..7

..4..x..9..x.10..x....9..x.10..x.11..x....3..x..6..x..8..x....1..x..9..x.11..x

..x..7..x..8..x.11....x..3..x..5..x..8....x..5..x..9..x.11....x..4..x..8..x.10

CROSSREFS

Sequence in context: A230349 A158601 A268738 * A130832 A180810 A109116

Adjacent sequences:  A215287 A215288 A215289 * A215291 A215292 A215293

KEYWORD

nonn

AUTHOR

R. H. Hardin Aug 07 2012

STATUS

approved

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Last modified December 5 10:11 EST 2021. Contains 349543 sequences. (Running on oeis4.)