Ashbaugh–Benguria eigenvalue-sum conjecture for Euclidean domains

Let $\Omega$ be a bounded domain in Euclidean space $\mathbb{R}^{n}$, and let $\lambda_i$ be the $i$-th Dirichlet eigenvalue of the Laplacian on $\Omega$. Let $\mathbb{B}^{n}$ be a ball with the same volume as $\Omega$, so that $\operatorname{vol}(\Omega)=\operatorname{vol}(\mathbb{B}^{n})$. Ashbaugh–Benguria conjecture.

$$\lambda_{2}+\lambda_{3}+\cdots+\lambda_{n+1}\leq n\frac{\lambda_{2}(\mathbb{B}^{n})}{\lambda_{1}(\mathbb{B}^{n})}\lambda_{1}.$$

This conjecture concerns sharp universal bounds for sums of Dirichlet eigenvalues; the supplied source states that it has been solved.