Number of times a code is executed

Question

I have a piece of code that says:

for i = 4,16, . . . , n

I am trying to find an upper bound in terms of big oh notation for the number of times the statement gets executed. I believe here it goes like 4,4²,4³ ... and so on. Since it grows exponentially, it looks like to me that that code is executed about O(logn) times. Am i right? Thanks in advance.

Answer 1

You can confirm your result by thinking in terms of a loop whose index variable is used as the exponent, taking the values 1, 2, 3, ... , floor(log_4(n))