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

According to Wikipedia, there are some double exponential time problems O(2^2poly(n)) which is more complex than O(nⁿ), e.g. "Decision procedures for Presburger arithmetic" (O(2^2cn)) and "Computing a Gröbner basis" (in worst case O(2^2n/10)