Which of the following is an example of a non-linear recurrence?
an=an−1+3a_n = a_{n-1} + 3an=an−1+3
an=an−12+1a_n = a_{n-1}^2 + 1an=an−12+1
an=2an−1+na_n = 2a_{n-1} + nan=2an−1+n
an=sin(an−1)a_n = \sin(a_{n-1})an=sin(an−1)