Euler totient function
Rule
Each term is: The number of integers less than the number that are coprime to the number
Known as: Euler totient function
The number of integers less than a number that are coprime to the number; ie they share no factors. Also called phi(n).
Named after the Swiss mathematician Leonhard Euler, who studied it.
The first 50 terms (starting from n=1) are:
1 1 2 2 4 2 6 4 6 4 10 4 12 6 8 8 16 6 18 8 12 10 22 8 20 12 18 12 28 8 30 16 20 16 24 12 36 18 24 16 40 12 42 20 24 22 46 16 42 20
Example
To get the value for n=24:
- Find the integers less than the number that are coprime to the number, giving 1, 5, 7, 11, 13, 17, 19, 23
- Count them, giving 8.
So the result is 8.