SQL & PL/SQL

I gave myself a small puzzle, to try to get the numbers 1-5 repeating as many times as their values: 1, 2, 2, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 5

My first attempt was quite simple. But i do not understand the results. Can someone explain to me why these are the results?

SQL> SELECT
  2     Rownum,
  3     A
  4  FROM
  5     (SELECT Rownum A FROM Dual CONNECT BY Rownum <= 5)
  6  CONNECT BY
  7     Rownum <= A;

    ROWNUM          A
---------- ----------
         1          1
         2          2
         3          3
         4          4
         5          5
         6          2
         7          3
         8          4
         9          5

9 rows selected.