The Franklin magic square is a 8x8
semimagic square with a magic constant
of 260. It was constructed by Benjamin Franklin in 1750. Besides the
usual sum of the numbers in the rows equal the magic constant which in this case is 260, this semimagic square also has the sum of each half row or column equal to 130. On top
of that, the four corners plus the 2x2 square in the middle add up to 260
and bent diagonals also equate to 260 (half way one diagonal line, then
goes the other half way on a line perpendicular to the one it was already
on). Franklin explained the reason for this invention in 1771 to be, "I
was at length tired with sitting there to hear debates, in which, as
clerk, I could take no part, and which were often so unentertaining that I
was induc'd to amuse myself with making magic squares or circles."
