Final answer:
The rule that represents this function is: y = 4^x.
Step-by-step explanation:
The ordered pairs (0, 1), (1, 4), (2, 16), (3, 64), and (4, 256) represent a function. To find a rule that represents this function, we need to observe the pattern in the y-values as x increases. In this case, we notice that the y-value is equal to 4 raised to the power of x. Therefore, the rule that represents this function is:
y = 4^x