Question: Which episode was N/A in region 1
SQL: SELECT "Episodes" FROM "1-15823956-1" WHERE "Region 1" = 'N/A';

Question: When was series premiere on the Pilot episode
SQL: SELECT "Series premiere" FROM "1-15823956-1" WHERE "Series" = 'Pilot';

Question: What is the region 1 date for series 4
SQL: SELECT "Region 1" FROM "1-15823956-1" WHERE "Series" = '4';

Question: How many episodes in the series that premieres 5 February 2012
SQL: SELECT "Episodes" FROM "1-15823956-1" WHERE "Series premiere" = '5 February 2012';