using System;

public class Program

{

    public static void Main()

    {

        var maxRetries = 5;

        var nextRetry = DateTime.UtcNow;

        Console.WriteLine($"First attempt:\t {nextRetry.ToString("o")}");

        for (var retryCount = 0; retryCount < maxRetries; retryCount++)

        {

            var prevRetry = nextRetry;

            nextRetry = nextRetry.AddSeconds(30 * Math.Pow(2, retryCount));

            Console.WriteLine($"Next retry:\t\t{nextRetry.ToString("o")} ({nextRetry - prevRetry})");

        }

    }

}