What do you mean with "not inserting sequentially"? A table has no order of its rows unless you use an ORDER BY clause. So you could sort on the generated column.
If you are referring to gaps in the generated values, you cannot avoid that anyway: a transaction could do an insert and then rollback. The generated value is used but doesn't occur in any row in the table after the rollback. (If you rely on there being no gaps, you should revisit your design - usually, it has a problem. I know that there are sometimes legal requirements that you must not have gaps. In that case, generated values are not the way to go.)