1) Writing a Recursive rule for that Arithmetic Sequence
Let's firstly pick the first element, a recursive rule depends on the previous element.
f(1) = 8
2) Looking at the Sequence, the common ratio is 8
f(1)= 8
f(3+1)
f(4) = 8 +(3-1)*8
f(2) = 8 +(2)8
f(2) = f(3)
For n > 1
f(2) = f(1) +8
So f(n) = f(n-1) +8