Answer
$a_{n}=\displaystyle \frac{n+1}{n+2}$
Work Step by Step
The numerators progress as
first term : 2
second term : 3
third term : 4
...
n-th term: (n+1)
The denominators progress as
first term : 3
second term : 4
third term : 5
...
n-th term: (n+2)
$a_{n}=\displaystyle \frac{n+1}{n+2}$
