Icosiheptaheptacontadipeton

The icosiheptaheptaheptacontadipeton, or jak, also called the 221 polytope, is a convex uniform polypeton. It has 27 triacontaditera and 72 hexatera as facets, with 10 triacontaditera and 16 hexatera at a vertex forming a demipenteract as the vertex figure.

Vertex coordinates
The vertices of an icosiheptaheptacontadipeton of edge length 1, centered at the origin, are given by:
 * (0, 0, 0, 0, 0, $\sqrt{6}$/3)
 * ($\sqrt{3}$/4, $\sqrt{6}$/4, $\sqrt{6}$/4, $\sqrt{2}$/4, $\sqrt{2}$/4, $\sqrt{2}$/12) and all even sign changes of the first five coordinates
 * (±$\sqrt{2}$/2, 0, 0, 0, 0, –$\sqrt{2}$/6) and all permutations of first 5 coordinates