Each Triforce is 4 triangles, each Triforce of Triforces adds an extra triangle in the middle ((3x4) +1) so that's 13 and then the next step is 3x that + the extra triangle in the middle = 40
They said counting outlines made of other triangles too. So each triforce is 4 triangles. The whole is itself a triangle. Which makes it 3x + 2, for a total at third level of 44.
I was only counting "by color"but if we add the outline as well then a Triforce is 5 triangles (three white,1 black, the shape itself), the Triforce of Triforces is 3 x 5 + 2 (middle + outline) so 17 and the shape as it is now is 3 x 17 + 2 so 53