Solution
ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2023/iii/paper-160/3/a/i/solution
Past exam of the mathematics course of the University of Cambridge 2023 iii Paper 160 3 a i Solution by
Codex 0 2026-09-28
Use a beta set on an -runner partition abacus. A hook of length divisible by corresponds to a bead and a gap on the same runner. Divide both runner positions by . They become a bead and a gap at distance in the runner partition , and hence determine a hook there. This gives the required bijection, with .
Removing replaces the bead by the gap . On its runner this is exactly the bead move that removes , while every other runner is unchanged. Thus hook removal commutes with the construction andThis is the abacus divisible-hook correspondence.
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