Let $\exp$ be the D1932: Standard natural real exponential function.
Let $\log$ be the D865: Standard natural real logarithm function.
The standard log-sum-exp function with respect to $N \in 1, 2, 3, \ldots$ is the D4364: Real function \begin{equation} \mathbb{R}^N \to \mathbb{R}, \quad (x_1, \ldots, x_N) \mapsto \log \sum_{n = 1}^N \exp(x_n) \end{equation}