Which of these is a linear recurrence?
an=2an−1+1a_n = 2a_{n-1} + 1an=2an−1+1
an=an−1+n2a_n = a_{n-1} + n^2an=an−1+n2
an=3an−1+an−2a_n = 3a_{n-1} + a_{n-2}an=3an−1+an−2
All of the above