Denote by $\mathfrak{c}^+$ the cardinal successor of continuum. Can we prove in $\mathsf{ZFC}$ that
$(\mathfrak{c}^+)^{\aleph_0} = \mathfrak{c}^+$?
I guess not. Of course this question is trivial for $2^{\mathfrak{c}}$ yet I don't want to assume any sort of $\mathsf{GCH}$.
Yes we can and it is an easy application of the Hausdorff formula.
Specifically, since $\mathfrak{c}^+$ is regular, any function from $\omega$ to $\mathfrak{c}^+$ is bounded. Any such function is then determined by an upper bound below $\mathfrak{c}^+$ and a function from $\omega$ into $\mathfrak{c}$, and this shows that $(\mathfrak{c}^+)^{\aleph_0}\leq \mathfrak{c}^+\cdot \mathfrak{c}^{\aleph_0}=\mathfrak{c}^+$. Equality then follows by Cantor-Schröder-Bernstein.