create table t1 (c2 int as (-c1), c1 int primary key auto_increment) engine=innodb;
insert into t1(c1) values (null),(null),(null);
select * from t1;
c2	c1
-1	1
-2	2
-3	3
alter table t1 auto_increment = 3;
show create table t1;
Table	Create Table
t1	CREATE TABLE `t1` (
  `c2` int(11) AS (-c1) VIRTUAL,
  `c1` int(11) NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`c1`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=latin1
drop table t1;