Try this,
declare @ds varchar(25)
set @ds = CONVERT(CHAR(10), GETDATE(),126)
set @ds = LEFT(@ds, LEN(@ds) - 6)
set @ds = RIGHT(RTRIM(@ds), 2)
if (select count(*) from [Table_2] where LEFT(col1,2) = @ds ) > 0
select @ds+ '/' + RIGHT('0000' + CONVERT(VARCHAR(5),MAX(CAST(RIGHT(col1,5)AS INT))+ 1),5) DC_No from [Table_2]
Else
select @ds+ '/' + '00001' DC_No