I made this to go with pattern 38 at visualpatterns.org, Fawn Nguyen's excellent site. http://www.visualpatterns.org/#!21-40/czdm How many triangles in each step? Are you counting all of them or just one orientation? All the sizes? There's a lot to look at. Can you come up with a rule? I added some bells and whistles because ... why not? How would you generalize this?
More GeoGebra at mathhombre.blogspot.org.