user: Question: What was the production code of the episode no. 55 in the series?
Columns: ['No. in series', 'No. in season', 'Title', 'Directed by', 'Written by', 'Original air date', 'Production code', 'U.S. viewers (million)']
Types: ['real', 'real', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: [47.0, 1.0, '"Red Sky at Night"', 'Chris Long', 'Bruno Heller', 'September23,2010', '3X6401', '15.50']
SQL:

assistant: SELECT "Production code" FROM "Table" WHERE "No. in series" = 55.0;