fareylen — returns the length of a Farey Sequence.
This opcode can be used in conjunction with GENfarey. It calculates the length of Farey Sequence Fn. Its length is given by: |Fn| = 1 + SUM over n phi(m) where phi(m) is Euler's totient function, which gives the number of integers ≤ m that are coprime to m.
Some values for the length of Fn given n:
n | Fn |
---|---|
1 | 2 |
2 | 3 |
3 | 5 |
4 | 7 |
5 | 11 |
6 | 13 |
7 | 19 |
8 | 23 |
9 | 29 |
10 | 33 |
11 | 43 |
12 | 47 |
13 | 59 |
14 | 65 |
15 | 73 |
16 | 81 |
17 | 97 |
18 | 103 |
19 | 121 |
20 | 129 |