$a_n = a_{n-1} + 2$, $a_1 = 1$

$a_n = 2a_{n-1} + 1$, $a_0 = 1$

$a_n = a_{n-1} + 1$, $a_1 = 1$

$a_n = 2a_{n-1}$, $a_0 = 1$