WITH t AS
     (SELECT     LEVEL lv
            FROM DUAL
      CONNECT BY LEVEL < 19)
SELECT   MAX (val1) val1, MAX (val2) val2
    FROM (SELECT CASE
                    WHEN MOD (lv, 10) IN (1, 2, 3, 4, 5)
                       THEN lv
                    ELSE NULL
                 END val1
               , CASE
                    WHEN MOD (lv, 10) IN (6, 7, 8, 9, 0)
                       THEN lv
                    ELSE NULL
                 END val2
               , TRUNC ((lv - 1) / 10) grp1, decode(MOD (lv, 5),0,5,MOD (lv, 5)) grp2
            FROM t)
GROUP BY grp1, grp2
ORDER BY grp1, grp2

맞는지 모르겠네요. 실제 데이터 앞에 rownum 같은 걸로 순번 매기고 하시면 될 듯합니다.

WITH T AS (
    SELECT  CHR(64 + LEVEL) val
    FROM    dual
    CONNECT BY LEVEL <= 26
    ORDER BY LEVEL DESC
)
SELECT  val, lead_val
FROM    (
            SELECT  ROW_NUMBER() OVER (ORDER BY val) rn, -- 필요시 정렬 기준 변경
                    val,
                    LEAD(val, 5) OVER (ORDER BY val) lead_val -- 필요시 정렬 기준 변경
            FROM    t
        )
WHERE   MOD(TRUNC((rn - 1) / 5), 2) = 0

SELECT MIN(lv) c1
     , DECODE(COUNT(*), 2, MAX(lv)) c2
  FROM (SELECT LEVEL lv FROM dual CONNECT BY LEVEL <= 18)
 GROUP BY CEIL(lv / 10), MOD(lv,  5)
 ORDER BY c1
;