0.5x0.5 - 8 1x1 - 18 2x2 - 9 3x3 - 4 4x4 - 1 Total 40 outside frame= square - 1(tricky answer) total 41
It's 40. <iframe width="420" height="315" src="http://www.youtube.com/embed/vwLMmy5QLU8" frameborder="0" allowfullscreen></iframe>
The small squares form bigger squares, and the two squares floating in the squares are ventral points of two additional squares.