finite difference method

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

namespace ConsoleApplication3
{
    class Program
    {
        static void Main(string[] args)
        {
            double[] dy = { 12.4, 45.6, 10, 45.1, 76.1 };
            int l = dy.Length;
            double[,] dyy = new double[l,l];

            for (int i = 0; i < l; i++)
                dyy[0, i] = dy[i];

            for (int i = 1; i < l; i++)
            {
                for (int j = 1; j < l - i + 1; j++)
                    dyy[i, j - 1] = dyy[i - 1, j] - dyy[i - 1, j - 1];
            }

            for (int i = 0; i < l; i++)
            {
                for (int j = 0; j < l-i; j++)
                {
                    Console.Write(dyy[i, j] + "; ");
                }
                Console.Write("\n");
            }
            Console.ReadLine();
        }
    }
}