using System;

using System.Linq;

using System.Text;

public class Program

{

    public static void Main()

    {        

            var num = 5; // cambiar aqui

            var sb = new StringBuilder();

​

            Enumerable.Range(1, num).Select((value, index) => new { index, elements = Enumerable.Range(1, index) })

                .ToList()

                .ForEach(item => {

                    sb.Append(new string(' ', num - item.index));

                    sb.Append(string.Join("", item.elements));

                    sb.Append(string.Join("", item.elements.Reverse().Skip(1)));

                    sb.AppendLine("");

            });

​

            Console.WriteLine(sb.ToString());

    }

}