List of top Quantitative Aptitude Questions on Number Series

Find the missing number in the series: \(2, 6, 12, 20, 30, \_\_\).
Complete the series: \(285,\,253,\,221,\,189,\,?\)
Given the sequence of numbers 2, 3, 5, 7, 11, 13, 17, 19, 23, _ _ _ _ _. What are the next two numbers?
The 20th term in the triangular numbers 1, 3, 6, 10, 15, 21, ... is