For the series: 1, 3, 7, 13, 21, ?, what comes next?
Q1. For the series: 1, 3, 7, 13, 21, ?, what comes next?
Answer: 31
Explanation: The differences between terms are 2, 4, 6, 8, 10, ... so the next difference is 12, making the next number 21 + 10 = 31.