DECLARE @startnum INT=1000
DECLARE @endnum INT=1004
;
WITH gen AS (
    SELECT @startnum AS num
    UNION ALL
    SELECT num+1 FROM gen WHERE num+1<=@endnum
)
SELECT * FROM gen
option (maxrecursion 0)

select a1.*, a2.*
from
(select
      1000 as v1
union all
select
      1001 as v1
union all
select
      1003 as v1)a1
left join
(select
      1000 as v2
union all
select
      1001 as v2
union all
select
      1003 as v2
union all
select
      1004 as v2)a2
    ON a1.v1=a2.v2

DECLARE @startnum INT=1000
DECLARE @endnum INT=1004
;
WITH gen AS (
    SELECT @startnum AS num
    UNION ALL
    SELECT num+1 FROM gen WHERE num+1<=@endnum
),cte as
(
SELECT * FROM gen

) , cte1 as
(
select a1.* from
(select
      1000 as v1
union all
select
      1001 as v1
union all
select
      1003 as v1
      )a1

) select cte.*,cte1.* from cte join cte1 on cte.num=cte1.v1

WITH gen AS (
      SELECT @startnum AS num
      UNION ALL
      SELECT num + 1
      FROM gen
      WHERE num + 1 <= @endnum
     )
SELECT
FROM gen JOIN
     a1
     ON a1.v1 = gen.num
OPTION (MAXRECURSION 0);