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A215289
Number of permutations of 0..floor((n*5-1)/2) on even squares of an nX5 array such that each row and column of even squares is increasing
1
1, 10, 140, 2100, 60060, 1051050, 42882840, 814773960, 41227562376, 824551247520, 48236247979920, 999179422441200, 64899082486180800, 1379105502831342000, 96951116849043342600, 2100607531729272423000, 157112712418611824074200
OFFSET
1,2
COMMENTS
Column 5 of A215292
LINKS
FORMULA
f3=floor((n+1)/2)
f4=floor(n/2)
a(n) = A060854(3,f3)*A060854(2,f4)*binomial(3*f3+2*f4,3*f3)
EXAMPLE
Some solutions for n=5
..0..x..2..x..6....1..x..2..x..6....0..x..3..x..9....0..x..1..x..8
..x..3..x..4..x....x..0..x..4..x....x..2..x..4..x....x..3..x..6..x
..1..x..7..x.10....7..x..9..x.11....1..x..7..x.11....2..x..4..x..9
..x..5..x.11..x....x..3..x..5..x....x..5..x..8..x....x..7..x.10..x
..8..x..9..x.12....8..x.10..x.12....6..x.10..x.12....5..x.11..x.12
CROSSREFS
Sequence in context: A089834 A132505 A254336 * A319578 A051618 A295034
KEYWORD
nonn
AUTHOR
R. H. Hardin Aug 07 2012
STATUS
approved