The sequence switches between two rules.
Questions:
Q1: What comes next? 2, 6, 4, 8, 6, 10, ___
Q2: What comes next? 1, 4, 2, 5, 3, ___
Q3: What comes next? 10, 5, 8, 4, 6, ___
Q4: What comes next? 30, 15, 18, 9, 12, ___
Q5: What comes next? 5, 10, 9, 18, 17, ___