Program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp2
{
    class Program
    {
        public static bool IsPrime(int n)
        {
            if (n < 4)
            {
                return true;
            }

            for (int i = 2; i * i <= n; i++)
            {
                if (n%i==0) return false;
            }

            return true;
        }
        static void Main(string[] args)
        {
            Array.ForEach(Enumerable.Range(2, Int32.MaxValue - 2)
                .Where(IsPrime)
                .Take(20)
                .Select(x => x * x)
                .Reverse().ToArray(), Console.WriteLine);
        }
    }
}