insert into dbo.t (id, col) 
  values (next value for dbo.seq, 'val'); 

use tempdb;
go

create sequence dbo.seq1 as int start with 1;
create table dbo.t (id int constraint PK_t primary key, v int);
alter table dbo.t add constraint DF_t__id default (next value for dbo.seq1) for id;
go

insert into dbo.t (v) values (1), (2);
select * from dbo.t;
go

drop table dbo.t;
drop sequence dbo.seq1;
go