Sequences as Functions and Recursion Practice Test

A sequence can be viewed as a discrete function whose domain is the positive integers. For the Fibonacci sequence defined by $f(1)=f(2)=1$ and $f(n)=f(n-1)+f(n-2)$ for $n\ge 3$, find $f(7)$.

The sequence $1,3,9,27,81,\dots$ is a function with domain $n\in{1,2,3,\dots}$. Which recursive definition matches this sequence?