select nextval('sequence') is the format that postgresql expects. If you look more closely at the instances where we use sequence.nextval in tcl, the calling routines do a regsub on sequence.nextval and convert it to nextval('sequence') before passing it to the postgresql driver. This is just a shortcut to save us from having to port all of those nexval statements.
You can fake the oracle syntax using a view:
create sequence sequence_name_t start 1;
create view sequence_name as
select nextval('sequence_name_t') as nextval;
