Which function forms an arithmetic sequence when x = 1, 2, 3,

The process of recursion can be thought of as climbing a ladder.
To get to the third rung, you must step on the second rung. Each rung on the ladder depends upon stepping on the rung below it.You start on the first rung of the ladder. a1
From the first rung, you move to the second rung. a2
    a2 = a1 + "step up"
From the second rung, you move to the third rung. a3
    a3 = a2 + "step up" so tell me if i helped