Circumscribable stars, inspired by a Malke Rosenberg post, http://mathinyourfeet.blogspot.com/2012/08/stars-factoring-patterns.html, which was inspired by a Vi Hart video, http://youtu.be/CfJzrmS9UfY.
There are many geometric and numeric patterns to notice here. The importance of factors and multiples is a great connection in the geometric patterns.
More GeoGebra at http://mathhombre.blogspot.com