SQL> DEFINE N=3
SQL> SELECT ROWNUM 
  2  FROM ( SELECT 1 FROM DUAL GROUP BY CUBE(1,2,3,4,5,6,7,8,9,10) )
  3  WHERE ROWNUM <= &N
  4  /
    ROWNUM
----------
         1
         2
         3

SQL> SELECT * 
  2  FROM ( SELECT ROWNUM FROM DUAL CONNECT BY LEVEL <= &N )
  3  /
    ROWNUM
----------
         1
         2
         3

SQL> SELECT ROWNUM FROM DUAL CONNECT BY LEVEL <= &N;
    ROWNUM
----------
         1
         2
         3

SQL> create or replace type row_table as table of number;
  2  /

Type created.

SQL> Create or replace function gen_row (num_rows in number) 
  2  return row_table 
  3  parallel_enable pipelined is 
  4  begin 
  5    for x in 1..num_rows loop
  6      pipe row (x);
  7    end loop;
  8    return;
  9  end; 
 10  / 

Function created.

SQL> select * from table(gen_row(&N)); 
COLUMN_VALUE
------------
           1
           2
           3

3 rows selected.

SQL> define n=5
SQL> select to_number(column_value) colval
  2  from xmltable('for $i in 1 to &n return $i');

    COLVAL
----------
         1
         2
         3
         4
         5

SQL > select integer_value
  2   from   dual
  3  where  1=2
  4  model
  5  dimension by ( 0 as key )
  6  measures     ( 0 as integer_value )
  7  rules upsert ( integer_value[ for key from 1 to 5 increment 1 ] = cv(key) );

INTEGER_VALUE
-------------
            1
            2
            3
            4
            5

SQL> select rownum from all_objects where rownum<=5;

    ROWNUM
----------
         1
         2
         3
         4
         5

SQL> select val
  2  from (select 1 rn from dual)
  3  model
  4    dimension by (rn)
  5    measures (1 val)
  6  rules 
  7    iterate (&N)
  8    ( val[iteration_number] = iteration_number+1 )
  9  order by val
 10  /
       VAL
----------
         1
         2
         3
         4
         5