public static IObservable <TOutput> ExecuteSequentally <TInput, TOutput>(this RxAction <TInput, TOutput> action, params TInput[] inputs) => action.executeSequentally(inputs);
public static IObservable <Unit> ExecuteSequentally(this RxAction <Unit, Unit> action, int times) => action.executeSequentally(Enumerable.Range(0, times).Select(_ => default(Unit)));
public static IObservable <TOutput> ExecuteSequentally <TInput, TOutput>(this RxAction <TInput, TOutput> action, IEnumerable <TInput> inputs) => action.executeSequentally(inputs);