using Combinatorics.Collections;

using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

        public static void Main(string[] args)

        {

            int[] max_bounds = new int[] { 1, 2, 3 };

            foreach (int[] pattern in GetPatterns(max_bounds))

                Console.WriteLine(string.Join(null, pattern));

        }

​

        private static IEnumerable<int[]> GetPatterns(int[] maxBounds)

        {

            for (int i = 0; i <= maxBounds.Length; i++)

            {

                Combinations<int> combinations = new Combinations<int>(Enumerable.Range(0, maxBounds.Length), i, GenerateOption.WithoutRepetition);

                foreach (IReadOnlyList<int> combo in combinations)

                {

                    int[] pattern = new int[maxBounds.Length];

                    combo.ToList().ForEach(j => pattern[j] = 1);

                    yield return pattern;

                    int k = 0;

                    while(k < combo.Count)

                    {

                        pattern[combo[k]]++;

                        if (pattern[combo[k]] <= maxBounds[combo[k]])

                            yield return pattern;

                        else

                            pattern[combo[k++]]--;

                    }

                }

            }

        }

}