Let \begin{align} c_k:=\sum_{n=1}^k \sum_{k=k_1+\dotsb+k_n}\frac{1}{n!}\frac{1}{k_1\cdots k_n} \end{align} where the second sum is over positive integers $k_j$. I need to prove that $\sqrt[k]{c_k}\to1$ as $k\to\infty$.
To simplify the problem one might consider the obvious bound \begin{align} \sum_{n=1}^k \sum_{k=k_1+\dotsb+k_n}\frac{1}{n!}=\sum_{n=1}^k \frac{1}{n!}\binom{k-1}{n-1}. \end{align}