row generator using recursive subquery factoring (recursive with / recursive CTE) in Oracle. More: http://docs.oracle.com/cd/E11882_01/server.112/e26088/statements_10002.htm#BABCDJDB

rowgen.sql

WITH RecursiveCTE (rnum) AS
(
    SELECT 1 AS rnum 
    FROM dual
    UNION ALL
    SELECT rnum + 1
    FROM RecursiveCTE
    WHERE rnum < 24
)
SELECT rnum
FROM RecursiveCTE;


      RNUM
----------
	 1
	 2
	 3
	 4
	 5
	 6
	 7
	 8
	 9
	10
	11
	12
	13
	14
	15
	16
	17
	18
	19
	20
	21
	22
	23
	24

24 rows selected.