Lets say each member recruits 5 members and it takes 6 months for a new member to recruit another 5 members. If we start with 100 people we end up with these numbers :
2022-02 100
2022-08 600
2023-02 3,100
2023-08 15,600
2024-02 78,100
2024-08 390,600
2025-02 1,953,100
2025-08 9,765,600
2026-02...