When Vincennes is the county seat what is the area sq mi (km 2 ) (rank) ?
create table table_14253123_1 (area_sq_mi__km_2____rank_ varchar, county_seat varchar, PRIMARY KEY (area_sq_mi__km_2____rank_))
select area_sq_mi__km_2____rank_ from table_14253123_1 where county_seat = "vincennes"