fact: Definition F1 {X} (T : nat -> list X) := (fun n => let (n, m) := Cantor.of_nat n in nth_error (T n) m).
imports: Undecidability.L(Computability.MuRec) Undecidability.L.Datatypes(LNat LOptions LProd) Undecidability.Synthetic(DecidabilityFacts EnumerabilityFacts ListEnumerabilityFacts ReducibilityFacts) Undecidability.L.Datatypes.List(List_basics List_nat) Datatypes