I used to make these on my notebooks in high school. I'm so glad there's a node for them. The only thing I feel should be added is that this continuing shape (where you draw little triangles out from the middles of the sides of the big one, with their sides 1/3 the length of the original, and then repeated that operation over and over again) is one of few examples of an infinite line enclosing a finite area. If you draw a circle around the original triangle, the continuous figure you end up drawing will never enclose more space than that circle, and yet the line around the outside of the figure is infinite in length, as long as you keep generating it by adding more little triangles to the sides. It always approaches the amount of area tha the circle has, but it'll never get there. It's asymptotic.

Thanks for the node; you got my vote.