No. Quick version: They have the same type. Both take an integer and return a string, so their type would be Integer -> String in your example.

They are computationally equivalent in the sense that they produce the same result given the same input, but they do not perform the exact same computation under the hood (the array is not syntactic sugar for the function).

For the distinction there, consider the two conventional forms of Fibonacci. Naive recursive (computationally expensive) and linear (computationally cheap). They perform the same computation (given sufficient memory and time), but they do not perform it in the same way. The array doesn't "desugar" into the function you wrote, but they are equivalent in that (setting aside call syntax versus indexing syntax) you could substitute the array for the function, and vice versa, and get the same result in the end.