This is the smaller 8x8 magic square of Benjamin Franklin. The spreadsheet (in Lotus123 WK4) formate can be downloaded for ease in playing with the properties listed below Ben's magic square.
All the rows and columns sum to the number 260, but that is not all. Half rows and half columns sum to 130.
The four entries in every 2x2 subsquare sum to 130.
But there is even more!
In the figures below, the bent diagonals going from top to bottom (Figure 1) sum to 260. Even the broken ones that have two pieces! Follow the colored patterns and you will be able to check this. (Each bent diagonal or broken diagonal should have 8 cells.) The other three figures show the other diagonals going from from right to left (Figure 2), from bottom to top (Figure 3) and from left to right (Figure 4) also have sums of 260.
These are not the only combinations that sum to 260. For an animated view of the combinations I have found so far that sum to 260, click here. The combinations will amaze you.
Please pause for a moment and reflect on the fact that this magic square was constructed over 200 years ago. Even with the aid of a computer this would be a prodigious task.