  Let $\Omega\subset \mathbb R^d\,, d\geq 2$, be a bounded open set, and denote
by $\lambda\_j(\Omega), j\geq 1$, the eigenvalues of the Dirichlet Laplacian
arranged in nondecreasing order, with multiplicities. The weak form of
Pleijel's theorem states that the number of eigenvalues $\lambda\_j(\Omega)$,
for which there exists an associated eigenfunction with precisely $j$ nodal
domains (Courant-sharp eigenvalues), is finite. The purpose of this note is to
determine an upper bound for Courant-sharp eigenvalues, expressed in terms of
simple geometric invariants of $\Omega$. We will see that this is connected
with one of the favorite problems considered by Y. Safarov.
