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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 October 15 10:15 EDT 2019. Contains 328026 sequences. (Running on oeis4.)