Question 65
The positive integers are grouped as follows:
$$
A_{1} = \{1\}, \quad A_{2} = \{2, 3, 4\}, \quad A_{3} = \{5, 6, 7, 8, 9\}, \text{ and so on. }
$$
In which group does $2009$ belong to?
$$
A_{1} = \{1\}, \quad A_{2} = \{2, 3, 4\}, \quad A_{3} = \{5, 6, 7, 8, 9\}, \text{ and so on. }
$$
In which group does $2009$ belong to?