using System;

public class Program

{

    public static void Main()

    {

    int loopLimit = 18;

    int n1, n2 = 2, n3 = 2;

    // Top Triangle nested for loop

    for (n1 = 0; n1 <= 18; n1++)

    {

        n2 = 2;

        while (n2 <= n3)

        {

            if (n2 <= loopLimit)

                Console.Write("{0} ", n2);               

            n2 += 2;

        };

        if (n2 > loopLimit)

            loopLimit -= 2;

        n3 += 2;

        Console.WriteLine();

    }

​

​

    }

}