n,portion
1,0.5
2,0.667
3,0.75
4,0.8
5,0.833
6,0.857
7,0.875
8,0.889
9,0.9
10,0.909
11,0.917
12,0.923
13,0.929
14,0.933
15,0.938
16,0.941
17,0.944
18,0.947
19,0.95
20,0.952
21,0.955
22,0.957
23,0.958
24,0.96
25,0.962
26,0.963
27,0.964
28,0.966
29,0.967
30,0.968