Sequence Generator Function in SQL

Here is the sequence generator function written in SQL, which when passed starting and end numbers will generate the rest sequence automatically.

CREATE FUNCTION fn_p(    @exp  int)
RETURNS @result TABLE (id int)
AS
BEGIN   
      DECLARE @pow int
     SET @pow = POWER(10, @exp)
     INSERT @result        SELECT 0 id UNION ALL         SELECT 1 * @pow UNION ALL        SELECT 2 * @pow UNION ALL        SELECT 3 * @pow UNION ALL        SELECT 4 * @pow UNION ALL        SELECT 5 * @pow UNION ALL        SELECT 6 * @pow UNION ALL        SELECT 7 * @pow UNION ALL        SELECT 8 * @pow UNION ALL        SELECT 9 * @pow    RETURNENDGO

CREATE FUNCTION fn_sequence
(    
@start int,   
@end  int
)
RETURNS @result TABLE(id int)
AS
BEGIN   
IF @start > @end
RETURN       
IF @end < 10       
INSERT @result        SELECT id FROM        (            SELECT                a0.id id            FROM                fn_p(0) a0        ) d        WHERE            id BETWEEN @start AND @end    ELSE
    IF @end < 100        INSERT @result        SELECT id FROM        (            SELECT                (a1.id + a0.id) id            FROM                fn_p(1) a1 CROSS JOIN                fn_p(0) a0        ) d        WHERE id BETWEEN @start AND @end    ELSE
    IF @end < 1000        INSERT @result        SELECT id FROM        (                SELECT                (a2.id + a1.id + a0.id) id            FROM                fn_p(2) a2 CROSS JOIN                fn_p(1) a1 CROSS JOIN                fn_p(0) a0        ) d        WHERE id BETWEEN @start AND @end            ELSE
    IF @end < 10000        INSERT @result        SELECT id FROM        (            SELECT                (a3.id + a2.id + a1.id + a0.id) id            FROM                fn_p(3) a3 CROSS JOIN                fn_p(2) a2 CROSS JOIN                fn_p(1) a1 CROSS JOIN                fn_p(0) a0        ) d        WHERE id BETWEEN @start AND @end     
    RETURNENDGO