If, in the definition of determinant, we replace multiplication with addition, then the result will always be 1. If we restrict ourselves to the 2x2 arrays whose diagonals lie on the main diagonal of the table, then the sum of four numbers in the array is always a complete square. As another generalization, consider the sum of elements in an off-diagonal 2x2 array. This is a composite number easily found from the row and column captions with the assistance of the distributive law . The same holds for higher order arrays.
Multiplication tables are rich in patterns.
Put your finger on an entry on the main diagonal. The entry you'll get is 1 less than the diagonal entry. Entries in the last row between columns 2 and 9 are mirror images of each other. In the last row, the sum of entries equidistant from columns 2 and 9 always sum up to 99. Looks like another case for the distributive law .