theorem
Hex.PermGroup.Group.derivedAt_spec
{n : ℕ}
(G : Group n)
(k : ℕ)
:
closure (G.derivedAt k).generators = Subgroup.map (closure G.generators).subtype (_root_.derivedSeries (↥(closure G.generators)) k)
Every computational series term is the image of the corresponding Mathlib derived-series subgroup under the ambient inclusion.
Solvability of the executable group is exactly Mathlib solvability of its generated subgroup; negative certificates therefore prove nonsolvability.