6.9Loops_PrintMatrixOfNumbers

using System;

class MatrixOfNumbers
{
    static void Main ()
    {
        Console.Write("Please, enter a whole positive number in the range [1...20], N = ");
        string numberStr = Console.ReadLine();
        int numN = int.Parse(numberStr);
        if (numN < 1 || numN > 20)
        {
            Console.WriteLine("Error - Invalid Number !!!");
        }
        else
        {
            Console.WriteLine("The matrix of numbers is:");
            Console.WriteLine();
            for (int i = 1; i <= numN; i++)
            {
                for (int j = i; j < numN + i; j++)
                {
                    Console.Write("{0,2} ", j);
                }
                Console.WriteLine();
            }
        }
        Console.ReadLine();
    }
}