Let $V \in \mathcal{M}_n(\mathbb{C})$ be a nilpotent matrix of index $p$. We propose to study the equation $R^2 = V$.
For every value of the integer $n \geqslant 3$, exhibit a matrix $V \in \mathcal{M}_n(\mathbb{C})$, nilpotent of index $p \geqslant 2$ and admitting at least one square root.