  We study Young's seminormal basis vectors of the dual Specht modules of the
symmetric group, indexed by a certain class of standard tableaux, and their
denominators. These vectors include those whose denominators control the
splitting of the canonical morphism $\Delta(\lambda+\mu) \to \Delta(\lambda)
\otimes \Delta(\mu)$ over $\mathbb{Z}_{(p)}$, where $\Delta(\nu)$ is the Weyl
module of the classical Schur algebra labelled by $\nu$.
