Note that the number of sequences for distance "d" is just the binomial coefficient formula_4 for L=3, and that each sequence can be visualized as the vertex of an L=3 dimensional cube, with each edge of the cube specifying a mutation path in which the change Hamming distance is either zero or ±1. It can be seen that, for example, one third of the mutations of the molecules will produce [000 molecules, while the other two thirds will produce the class 2 molecules and [101. We can now write the expression for the child populations formula_5 of class "i" in terms of the parent populations formula_6.