I don't see how that helps answer my problem. I know how to update a sequence. I want to pass a value for the restart vaue that depends on a query - all in one statement. I would think it is a common problem i.e. migrating data.
use a subquery to set the value -
select setval('foo', select max(some_id) from some_table)
It's all right there in the docs that you were pointed to. We try to encourage people to be somewhat self sufficient around here.