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

%I #9 Aug 12 2016 07:04:23

%S 1,4,36,648,19800,972000,69060600,6756825600,866219961600,

%T 140837901120000,28269530815680000,6865910948635200000

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

%C Column 2 of A268472.

%e Some solutions for n=4

%e ..3..1. .1..1. .2..1. .1..0. .0..0. .3..2. .0..3. .3..3. .2..2. .1..2

%e ..1..3. .0..3. .1..3. .2..3. .2..3. .0..3. .1..0. .2..0. .3..3. .0..0

%e ..0..0. .3..2. .3..2. .0..1. .1..2. .1..0. .3..1. .1..2. .1..1. .2..3

%e ..2..2. .2..0. .0..0. .3..2. .3..1. .2..1. .2..2. .0..1. .0..0. .3..1

%Y Cf. A268472.

%K nonn

%O 1,2

%A _R. H. Hardin_, Feb 05 2016