How many times is the formula tl 2 ba 2 cuo 6?
create table table_101336_1 (no_of_cu_o_planes_in_unit_cell varchar, formula varchar, PRIMARY KEY (no_of_cu_o_planes_in_unit_cell))
select no_of_cu_o_planes_in_unit_cell from table_101336_1 where formula = "tl 2 ba 2 cuo 6"