21-8 step prism

The 21-8 step prism is a convex isogonal polychoron, member of the step prism family. It has 84 phyllic disphenoids of two kinds as cells. Together with its dual, it is the sixth in an infinite family of triangular dihedral swirlchora.

Vertex coordinates
Coordinates for the vertices of a 21-8 step prism of circumradius $\sqrt{2}$ are given by: where k is an integer from 0 to 20.
 * (sin(2πk/21), cos(2πk/21), sin(16πk/21), cos(15πk/21)),