Jantzen-Seitz partitions are those p-regular partitions of~n which label
p-modular irreducible representations of the symmetric group Sn which
remain irreducible when restricted to Sn−1; they have recently also been
found to be important for certain exactly solvable models in statistical
mechanics. In this article we study their combinatorial properties via a
detailed analysis of their residue symbols; in particular the p-cores of
Jantzen-Seitz partitions are determined