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## Captions on this page:

A cellular automaton whose behavior seems neither highly regular nor completely random. The picture is obtained by applying the simple rule shown for a total of 150 steps, starting with a single black cell. Note that the particular rule used here yields a pattern that expands on the left but not on the right. In the scheme defined in Chapter 3, the rule is number 110.

More steps in the pattern shown above. Each successive page shows a total of 700 steps. The pattern continues to expand on the left forever, but only the part that fits across each page is shown. For a long time it is not clear how the right-hand part of the pattern will eventually look. But after 2780 steps, a fairly simple repetitive structure emerges. Note that to generate the pictures that follow requires applying the underlying cellular automaton rule for individual cells a total of about 12 million times.