Hurwitz orbits are the orbits of the braid group action on the powers of a rack. Hurwitz orbits for the action of the braid group on three strands are used in \cite{21} and \cite{22} for the classification of Nichols algebras... This classification is based on a combinatorial invariant called plague on the Hurwitz orbits. The method to calculate plagues on the Hurwitz orbits is formulated in \cite{22} by using a cellular automaton on the Hurwitz orbits and their quotients. By using this cellular automaton-based method we estimate the minimal plagues on the Hurwitz orbits. (read more)