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_name_17 ( song_sung VARCHAR, artist VARCHAR, week VARCHAR )

### Question ###
Which song was sung by Artist Luther Vandross in the Week Top 20?

### Accurate SQL ###

SELECT song_sung FROM table_name_17 WHERE artist = "luther vandross" AND week = "top 20"