The Design of Slowly Shrinking Labelled Squares
Elwyn R. Berlekamp · Mathematics of Computation · 1975
This paper considers the nonlinear operator T, which acts on 4-dimensional vectors with nonnegative real components. T transforms such a vector into a new vector whose components are the magnitudes of the differences of cyclically adjacent pairs of components of the previous vector. We show that T is not nilpotent.