Which of these is a homogeneous linear recurrence?
an=an−1+1a_n = a_{n-1} + 1an=an−1+1
an=3an−1+2an−2a_n = 3a_{n-1} + 2a_{n-2}an=3an−1+2an−2
an=an−1+na_n = a_{n-1} + nan=an−1+n
an=an−1+2na_n = a_{n-1} + 2^nan=an−1+2n