Definition s0 := (perm (inv_inj S0_inv)).Definition is_iso3 (p : {perm cube}) := forall fi, p (s0 fi) = s0 (p fi).Definition sop (p : {perm cube}) : seq cube := val (val (val p)).

Lemma seqs1 : forall f injf, sop (@perm _ f injf) = map f ecubes.