The answer is the fourth option - f(1) = 4 and f(n) = f(n − 1) + 2; n > 1
The first term is 4, So, f(1) = 4
The difference between two consecutive integer = 2, so, n = (n-1) + 2
It would be Option D) f(1) = 4 and f(n) = f(n − 1) + 2; n > 1
Hope this helps!