I'll just make a manual computation on how 1 member recruits his members until week 5. Then multiply the sum by 2.
old new
1: 1
2: 1 x 3 = 3 ⇒ 1 3 *only new members recruit 3 more
3: 3 x 3 = 9 ⇒ 4 9
4: 9 x 3 = 27⇒ 13 27
5: 27 x 3 = 81 ⇒ 40 81
40 + 81 = 121. Total number of members under 1 founding member.
121 x 2 founding members = 242 total number of members within 5 weeks.
The answer is 21.73684211
12. 15 (3x5x1)
13. 8 (4x2x1)
14. 18 (6x3x1)
Hope this helps! :D
So start with the top one and end w the bottom
