Page started - 12/2/99
Last updated - 20/6/99
Answer 10: Amnesty (part 1)
The cell must be a square number i.e. 1, 4, 9, 16, 25, 36, etc.Reasoning
For a cell to be left open, its key must be turned in the lock an odd number of times. Hence, the cell must have an odd number of factors. This can only happen if the number is a square, where one factor is its own compliment.