Subtract each number from the next. This is the series of "first differences" and it often gives a clue as to the rule used to generate the series. In this series, first differences are

1, 2, 3, 4, 5

We speculate that the next first difference will be 6, so the next term is

16 + 6 = 22

1, 2, 3, 4, 5

We speculate that the next first difference will be 6, so the next term is

16 + 6 = 22