A sponge is a solid which can be parameterized by Integers , , and which satisfy the equation
See also Honeycomb, Menger Sponge, Sierpinski Sponge, Tetrix
References
Ball, W. W. R. and Coxeter, H. S. M. Mathematical Recreations and Essays, 13th ed.
New York: Dover, p. 152, 1987.
Cromwell, P. R. Polyhedra. New York: Cambridge University Press, p. 79, 1997.