user: Question: When the # is 4, what is the pop./ km²?
Columns: ['#', 'Name', 'Name (English)', 'Population 2008-07-01', 'Area (km²)', 'Pop./ km²', 'ISO 3166-2', 'Administrative centre']
Types: ['real', 'text', 'text', 'real', 'real', 'text', 'text', 'text']
Sample row: [1.0, 'Höfuðborgarsvæði', 'Capital Region', 200969.0, 1062.0, '167.61', 'IS-1', 'Reykjavík']
SQL:

assistant: SELECT "Pop./ km²" FROM "Table" WHERE "#" = 4.0;