# No ABs in this string

A string of $$n$$ characters is made from the characters $$\text{A}$$, $$\text{B}$$, and $$\text{C}$$.

Let $$G_n$$ be the number of such strings of $$n$$ characters which contain no instance of $$\text{AB}$$ (in that order).

Write a recurrence relation for $$G_n$$.

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