Are there any real O(n^n) algorithms?

Question

Is there any real Algorithm with a time complexity O(n^n), that isn\'t just a gimmick?

I can create such an Algorithm, like computing n^n in O(n^n) / Θ(n^n):

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Answer 1

There are computations (for instance, tetration) where the output size is O(nⁿ). It's kind of hard to compute them with time complexity less than O(nⁿ).