This is either incorrect or it does not really mean anything, depending on how you look at it. It’s Stirling’s approximation, as the article mentions. The form

This is either incorrect or it does not really mean anything, depending on how you look at it. It’s Stirling’s approximation, as the article mentions. The formula uses the ≈ character. The Wikipedia article gives bounds on the error— https://en.wikipedia.org/wiki/Stirling's_approximation https://en.wikipedia.org/wiki/Stirling's_approximation