Run async tasks concurrently on Rx with maximum concurrent level

Program.cs

using System;
using System.Threading.Tasks;
using System.Reactive.Linq;

namespace rxconcurrent
{
    class Program
    {
        static void Main(string[] args)
        {
            var maxConcurrentLevel = 2;
            IObservable<long> ticks = Observable.Interval(TimeSpan.FromSeconds(0.1));
            ticks.Select(x => Observable.FromAsync(async () => 
                {
                    await Task.Delay(1000);
                    return x;
                }))
                .Merge(maxConcurrentLevel)
                .Subscribe(x => Console.WriteLine($"Tick! {x}"));

            Console.ReadKey();
        }
    }
}