How to generate Combinations without repetition recursively in C#

// 1: [0, 1]
// 2: [0, 2]
// 3: [0, 3]
// 4: [1, 2]
// 5: [1, 3]
// 6: [2, 3]

using System;

public static class CombinationsNoRep
{
    private static int numberofCombos;
    private static int n;
    private static int k;
    private static int[] storageArr;

    public static void Main()
    {
        n = 4;
        k = 2;
        storageArr = new int[k];

        GenCombinationsNoRep();
    }

    private static void GenCombinationsNoRep(int index = 0, int element = 0)
    {
        if (index >= storageArr.Length)
        {
            PrintCombo();
            return;
        }

        for (int i = element; i < n; i++)
        {
            storageArr[index] = i;
            GenCombinationsNoRep(index + 1, i + 1);
        }
    }

    private static void PrintCombo()
    {
            Console.WriteLine(
                "{0,3}: [{1}]", 
                ++numberofCombos, 
                string.Join(", ", storageArr));
    }
}