pb with sql hierarchical queries

HIERARCHY:

                                      1

           2                          3                          4

   5       6        7           8       9       10             11   12

 13 14    15 16   17 18               19 20     21             22

WHAT IS THE SQL CODE TO WRITE FOR OBTAIN IN HIERARCHICAL QUERIES THE FOLLOWING RESULT:

LEVEL 2       LEVEL4
2              13
2              14
2              15
2              16
2              17
2              18
3              19
3              20
3              21
4              22