Example of a O(2^N) algorithm [closed]

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I've been told that

O(2^N) denotes an algorithm whose growth will double with each additional element in the input data set

Can someone provide an example that behaves like this?

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Recursive computation of Fibonacci numbers is a good example of O(2^N) algorithm (though O(2^N) is not a tight bound for it):

public int fib(int n) {
    if (n <= 1) return n;
    else return fib(n - 2) + fib(n - 1);
}