Type-level recursion :)

Program.cs

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

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine(pt(5, 42));
        }

        static string pt<TC>(int depth, TC value)
        {
            if (depth == 0)
            {
                return value.ToString();
            }
            else
            {
                return pt<Pair<TC>>(depth - 1, new Pair<TC> { A = value, B = value });
            }
        }
    }

    class Pair<T>
    {
        public T A { get; set; }
        public T B { get; set; }

        public override string ToString()
        {
            return String.Format("Pair<{0} {1}>", A, B);
        }
    }
}