  After having translated the problem of solving the Rubik's Revenge in terms
of group actions, we use the result of the structure of the legal
transformations (Larsen) to count the states of the Rubik's Revenge modulo
legal and indistinguishable transformations, in the presence and absence of
mechanical constraints. We also find by a new method the computation made by
Bonzio, Loi and Peruzzi of the probability of being able to solve the Rubik's
Revenge after having assembled it randomly, once again in the presence and
absence of mechanical constraints.
