create table t (start1 number(3), total number(3));

insert into t values (4, 3);

insert into t values (9, 4);

  SELECT Distinct start1+LEVEL-1 myno
  FROM (select start1, total, start1+total-1 endno
  from t)
  CONNECT BY (start1+LEVEL-1) <= endno
 order by 1;

SQL> with
  2    t_numbers as (
  3      select start1+column_value-1 nb
  4      from t,
  5           table(cast(multiset (select level from dual connect by level <= total)
  6                      as sys.odciNumberList))
  7    ),
  8    all_numbers as (
  9      select level
 10      from dual
 11      connect by level < (select max(start1+total) from t)
 12    )
 13  select * from all_numbers
 14  minus
 15  select * from t_numbers
 16  /
     LEVEL
----------
         1
         2
         3
         7
         8

SQL> SELECT LEVEL num_list
  2  FROM   dual
  3  CONNECT BY LEVEL < (SELECT Max(start1 + total)
  4                      FROM   t)
  5  MINUS
  6  SELECT start1 + LEVEL - 1 myno
  7  FROM   (SELECT start1,
  8                 total,
  9                 start1 + total - 1 endno
 10          FROM   t)
 11  CONNECT BY ( start1 + LEVEL - 1 ) <= endno
 12  /
  NUM_LIST
----------
         1
         2
         3
         7
         8

with r(n,l) as (
                 select  start1 + total - 1 n,
                         total n
                   from  t
                union all
                 select n - 1 n,
                        l - 1 l
                   from  r
                   where l > 1
               )
select  n
  from  r
  order by n
/

         N
----------
         4
         5
         6
         9
        10
        11
        12

7 rows selected.

SQL>