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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
OFFSET
1,2
COMMENTS
Column 6 of A215292
LINKS
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: A158601 A268738 A358108 * A130832 A180810 A109116
KEYWORD
nonn
AUTHOR
R. H. Hardin Aug 07 2012
STATUS
approved