Algebraic forms [for cellular automaton rules]

The rules here can be expressed in algebraic terms (see page 869) as follows:

• Rule 30: Mod[p + q + r + q r, 2]

• Rule 45: Mod[1 + p + r + q r, 2]

• Rule 73: Mod[1 + p + q + r + p r + p q r, 2]