Proof Lei the magic sum of M be s. The half-columns and half-rows of T add up lo s since they are the columns and rows of M, respectively. Also the columns and rows of T add to 2s. The bent diagonals of T sum to 2s (see Figure 10 for an explanation). Since the 2 x 2 subsquares of M add to s/2, we infer that the 2 x 2 subsquares of T add to s/2. Thus T is a 16 x 16 Franklin square with magic sum 2s.