A215286 - OEIS

A215286

Number of permutations of 0..floor((n*n-1)/2) on even squares of an n X n array such that each row and column of even squares is increasing.

1, 2, 10, 280, 60060, 85765680, 2061378118800, 346915095471584640, 1736278161426147413954880, 62144711688730139887005809020800, 103104526145243794108489566205445861006400

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

COMMENTS

Diagonal of A215292.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..40

FORMULA

f1 = floor((n+1)/2)

f2 = floor(n/2)

T(n,k) = A060854(f1,f1)*A060854(f2,f2)*binomial(f1*f1+f2*f2,f1*f1).

EXAMPLE

Some solutions for n=5

..0..x..1..x..2....0..x..2..x..6....0..x..2..x..4....1..x..2..x..6

..x..4..x..7..x....x..1..x..3..x....x..3..x..5..x....x..0..x..8..x

..3..x..6..x..9....5..x..8..x.11....1..x..8..x..9....3..x..5..x.10

..x..5..x.11..x....x..4..x..9..x....x..7..x.10..x....x..9..x.12..x

..8..x.10..x.12....7..x.10..x.12....6..x.11..x.12....4..x..7..x.11

CROSSREFS

Cf. A060854, A215292.

Sequence in context: A074056 A206158 A144288 * A260231 A003047 A028580

Adjacent sequences: A215283 A215284 A215285 * A215287 A215288 A215289

KEYWORD

nonn

AUTHOR

R. H. Hardin, Aug 07 2012

STATUS

approved