Young's seminormal basis vectors and their denominators

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 $\nu$.