Concept:The series follows a pattern where each term is three less than a perfect cube, except one term.Explanation:Check each number against cubes:5=23−327=33 (not 33−3)61=43−3122=53−3213=63−3340=73−3509=83−3Thus, all numbers except 27 are of the form n3−3.Answer:27 is the odd one out.