See https://en.wikipedia.org/wiki/Euler%27s_totient_function */ public class EulersFunction { // This method returns us number of x that (x < n) and gcd(x, n) == 1 in O(sqrt(n)) time // complexity; public static int getEuler(int n) { int result = n; for (int i = 2; i * i 1) result -= result / n; return result; } public static void main(String[] args) { for (int i = 1; i < 100; i++) { System.out.println(getEuler(i)); } } }