For the recurrence an=nn+1an−1a_n = \frac{n}{n+1} a_{n-1}an=n+1nan−1 with a0=2a_0 = 2a0=2, compute a4a_4a4.
14\frac{1}{4}41
25\frac{2}{5}52
45\frac{4}{5}54
85\frac{8}{5}58