Connection [of geometric substitution systems] with digit sequences
Patterns after t steps can be viewed as containing all t-digit integers in an appropriate complex base. Thus the patterns on page 189 can be formed from t-digit integers in base - 1 containing only digits 0 and 1, as given by
Table[FromDigits[IntegerDigits[s, 2, t], - 1], {s, 0, 2t-1}]
In the particular case of base - q with digits 0 through q2, it turns out that for sufficiently large t any complex integer can be represented, and will therefore be part of the pattern. (Compare page 1094.)