Cellular Automata and Fractal Evolution

Cellular Automaton Basics - Number of CA Rules

We have already seen with S states per cell and N cells per nbhd, there are SN neighborhood configurations.

A rule specifies exactly which of the S possible states results from each of the SN neighborhood configurations.

Suppose we number the neighborhood configurations 1 through SN.

Then there are S outcomes for configuration 1 and S outcomes for configuration 2, so S2 combinations of outcomes for configurations 1 and 2.

For example, take S = 2, and write the states as 0 and 1. Then the combinations for the first two neighborhood configurations are

Continuing, there are S3 combinations of outcomes for configurations 1, 2, and 3.

For S = 2, here are the combinations for the first three neighborhood configurations

Because there are SN neighborhood configurations,

there are S(SN) rules.

How large is this number?

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