A 2 To solve this recurrence relation, it is convenient to write the following expansion: F n ~ ( s ) ≃ f n − s b n. A 3 Then F n ~ ( s = 0 ) = f n yields the extinction probability.
� + ϕ ) F n ( s ) ~ = ϕ F n − 1 ( s ) ~ + λ F n + 1 ( s ) ~.