using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var numRetries = 3;

        var retries = new List<double>();

        var timespans = new List<TimeSpan>();

        for (var i=0; i <= numRetries; i++)

        {

            retries.Add(Math.Pow(2, i));

            timespans.Add(TimeSpan.FromSeconds(Math.Pow(3, i)));

        }

​

        Console.WriteLine(string.Join(", ", retries.Select(x => x.ToString())));

        Console.WriteLine(string.Join(", ", timespans.Select(x => x.ToString())));

    }

}