user: Question: What is the original air date of the episode that was number 31 in the series? 
Columns: ['No. in series', 'No. in season', 'Title', 'Directed by', 'Written by', 'Original air date', 'Production code']
Types: ['real', 'real', 'text', 'text', 'text', 'text', 'real']
Sample row: [23.0, 1.0, '"Goliath (Part 1)"', 'Winrich Kolbe', 'Robert Foster & Robert Gilmer', 'October2,1983', 57875.0]
SQL:

assistant: SELECT "Original air date" FROM "Table" WHERE "No. in series" = 31.0;