# Euler's totient function

And now something completely different. Straight from the World of Number Theory.
Frankly, I just wanted to show off the powers of my new Estatico functionality
and give tribute to my all time hero **Leonhard Euler**.

## Definition 

For a given value _n_ this function returns the number of positive integers,
relatively prime to _n_ up to _n_.

## Computing

You can compute it for instance via _Euler's product formula_, multiplying 
over the distinct prime numbers dividing _p_:
$$\varphi(n) =n \prod_{p\mid n} \left(1-\frac{1}{p}\right)$$