many things

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+# 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_:
+$$\varphi(n) =n \prod_{p\mid n} \left(1-\frac{1}{p}\right)$$
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