https://preparationpoint.info/solved-past-papers-mcqs/ppsc-past-papers/ppsc-past-papers-2018/excise-taxation-inspector-bs-16-2018-in-additional-directorate-held-on-20-10-2018/complete-the-series-2-20-42-68-___/
Complete the series . 2 ,20 , 42 , 68, ___