Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_127511_1 ( sequencer VARCHAR, ion_torrent_pgm VARCHAR )

### Question ###
What is the sequencer when ion torrent pgm is 200-400 bp?

### Accurate SQL ###

SELECT sequencer FROM table_127511_1 WHERE ion_torrent_pgm = "200-400 bp"