Try like this
CREATE TABLE dbo.TestTable
( ID INT IDENTITY(1,1) PRIMARY KEY,
name int ,
FormatColumn AS RIGHT('LS_00' + CAST(ID AS VARCHAR(8)), 6) PERSISTED
)
insert into TestTable ( name) values (1)
insert into TestTable ( name) values (2)
insert into TestTable ( name) values (3)
select * from TestTable