43. (a) The central cell is on if exactly one of the left and right neighbors is on. As an outer totalistic rule, this is

(b) The central cell is on if exactly both of the left and right neighbors are on. As an outer totalistic rule, this is

(c) The central cell is on unless the left neighbor is off and the right neighbor is on. Unlike the other two examples, this is not an outer totalistic rule.

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