Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
How many times is the formula tl 2 ba 2 cuo 6?

### Inputs:
table_name: table, columns: ['Formula', 'Notation', 'T c (K)', 'No. of Cu-O planes in unit cell', 'Crystal structure']

### Response:
SELECT No. of Cu-O planes in unit cell FROM table WHERE Formula = Tl 2 Ba 2 CuO 6