Introduction to Lie Algebras and Representation Theory
《Introduction to Lie Algebras and Representation Theory》 · 第 138–139 页 · Chapter VII，Section 24.2「Kostant's multiplicity formula」，Theorem
Theorem (Kostant). Let $\Lambda \in \Lambda^+$. Then the multiplicities of $V(\Lambda)$ are given by the formula $m_\Lambda(\mu) = \sum_{\sigma\in\mathscr W} \operatorname{sn}(\sigma) p(\mu+\delta-\sigma(\Lambda+\delta))$.