input: Write a python function to group numbers with equal sums. 
  assert group_equal_sum([1, 2, 3, 4, 5, 6]) == [[1, 2, 3, 4, 5, 6]]
  assert group_equal_sum([3, 1, 2, 6, 4, 5]) == [[1, 2, 3, 4, 5, 6]]
  assert group_equal_sum([10, 12, 11, 13]) == [[10, 11, 12, 13]]
output: def group_equal_sum(lst):
      from itertools import combinations
      
      def sum_combinations(lst):
          result = {}
          for r in range(1, len(lst) + 1):
              for combo in combinations(lst, r):
                  combo_sum = sum(combo)
                  if combo_sum in result:
                      result[combo_sum].append(list(combo))
                  else:
                      result[combo_sum] = [list(combo)]
          return result
      
      sum_dict = sum_combinations(lst)
      max_length = max(len(groups) for groups in sum_dict.values())
      for groups in sum_dict.values():
          if len(groups) == max_length:
              return groups