A Room square (named after T. G. Room) of order (for even) is an arrangement in an square matrix
of objects such that each cell is either
empty or holds exactly two different objects. Furthermore, each object appears once
in each row and column and each unordered pair occupies exactly
one cell. The Room square of order 2 is shown below.
1,2
The Room square of order 8 is given in the following table.
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