(* Reduction from: Turing Machine Halting (HaltTM 1) to: Halting of one counter machines with denominators at most 4 (CM1_HALT) *)
(** ** HaltTM 1 reduces to CM1_HALT  *)
From Undecidability.FRACTRAN
From Undecidability.MinskyMachines
From Undecidability.CounterMachines

(* Many-one reduction from Turing machine halting to one counter machine halting (with denominators at most 4) *)
Theorem reduction : HaltTM 1 ⪯ CM1_HALT.