using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        foreach(var nr in nummerSerie().Take(4)){

            Console.WriteLine(nr);

        }

    }

    public static IEnumerable<int> nummerSerie(){

  int init = 1;

  int current = init;

  while(true){

    current *= 2;

    yield return current;

  }

}

}