Let $m \in \mathbb{N}$. We denote by $\mathcal{H}_m$ the vector subspace of harmonic polynomials of degree less than or equal to $m$. Determine the dimension of $\mathcal{H}_m$.
Let $m \in \mathbb{N}$. We denote by $\mathcal{H}_m$ the vector subspace of harmonic polynomials of degree less than or equal to $m$. Determine the dimension of $\mathcal{H}_m$.