A268470 Number of nX2 arrays containing 2 copies of 0..n-1 with column sums equal.

1, 4, 36, 648, 19800, 972000, 69060600, 6756825600, 866219961600, 140837901120000, 28269530815680000, 6865910948635200000

Offset

1,2

Comments

Column 2 of A268472.

Links

Table of n, a(n) for n=1..12.

Example

Some solutions for n=4
..3..1. .1..1. .2..1. .1..0. .0..0. .3..2. .0..3. .3..3. .2..2. .1..2
..1..3. .0..3. .1..3. .2..3. .2..3. .0..3. .1..0. .2..0. .3..3. .0..0
..0..0. .3..2. .3..2. .0..1. .1..2. .1..0. .3..1. .1..2. .1..1. .2..3
..2..2. .2..0. .0..0. .3..2. .3..1. .2..1. .2..2. .0..1. .0..0. .3..1

Crossrefs

Cf. A268472.

Sequence in context: A002084 A374859 A135867 * A365650 A214347 A208732

Adjacent sequences: A268467 A268468 A268469 * A268471 A268472 A268473

Keyword

nonn

Author

R. H. Hardin, Feb 05 2016

Status

approved