The figure on the main page is an arrangement of nine squares, each of which is a different size, which fit together to form a larger shape.
If you assume a side of the smallest square has a length of 1, the remaining squares have sides of length 4, 7, 8, 9, 10, 14, 15, and 18.

The larger shape formed is not a square but a 32x33 rectangle.

This figure was invented by Don Mittleman, Emeritus Professor of Mathematics at Oberlin College in Oberlin, Ohio, USA