SQL> create or replace function get_n (n integer)
  2    return sys.odcinumberlist
  3    pipelined
  4  is
  5  begin
  6    for i in 1..n loop
  7      pipe row (i);
  8    end loop;
  9  end;
 10  /

Function created.

SQL> select * from table(get_n(10));
COLUMN_VALUE
------------
           1
           2
           3
           4
           5
           6
           7
           8
           9
          10

10 rows selected.