PIMSO 2022 - Mathematics - Grade 10 / Secondary 4 - National Round Question 3

Consider the expression $\frac{2^{k_1}-2^{k_2}}{2^{k_3}-2^{k_4}}$ where $k_1,k_2,k_3,k_4$ are all non-negative integers. What is the smallest value of n where n represents the positive integers that cannot be equal to the expression?