Karl Reinhardt (mathematician)

Karl August Reinhardt (27 January 1895 Frankfurt am Main – 27 April 1941 Berlin) was a German mathematician who discovered the 5 tile-transitive pentagon tilings, solved the odd case of the biggest little polygon problem, and constructed the smoothed octagon conjectured to be the worst-packing point-symmetric planar convex shape. He also gave a partial solution to Hilbert's eighteenth problem by discovering an anisohedral tiling in three dimensions.