These are Sierpinski (pronounced sherpinski) tetrahedrons from order 0 to order 4. Each was derived from George Hart's original order 5 model (found at georgehart.com/rp/rp.html) by taking advantage of the self-similarity that characterizes fractals and simply removing successive layers. This was my very first adventure with Blender, otherwise I would have made the models scale invariant, as the iterative construction generally implies. I put these together because the original order 5 model is too empty to print when scaled to fit on the ABP. Interesting note: when the first layer composed of order 1 tetrahedrons is finished, the print is about half done, despite this only making up about 13% of the total height. Sincere thanks to George for freely providing such beautiful mathematical models!