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+package theweeklychallenge;
+
+/*
+
+Week 175:
+
+    https://theweeklychallenge.org/blog/perl-weekly-challenge-175
+
+Task #2: Perfect Totient Numbers
+
+    Write a script to generate first 20 Perfect Totient Numbers.
+
+Compile and Run:
+
+    mohammad-anwar/java$ javac theweeklychallenge/FirstPerfectTotient.java
+    mohammad-anwar/java$ java  theweeklychallenge.FirstPerfectTotient
+
+*/
+
+import java.util.Arrays;
+import java.util.ArrayList;
+import junit.framework.TestCase;
+import static junit.framework.Assert.*;
+
+public class FirstPerfectTotient extends TestCase {
+
+    public static void main(String[] args) {
+        junit.textui.TestRunner.run(
+            theweeklychallenge.FirstPerfectTotient.class);
+    }
+
+    public void testFirstPerfectTotient() {
+        Integer[] got = firstPerfectTotient(20);
+        Integer[] exp = {
+            3, 9, 15, 27, 39, 81, 111, 183, 243,
+            255, 327, 363, 471, 729, 2187, 2199,
+            3063, 4359, 4375, 5571
+        };
+
+        assertEquals(Arrays.toString(exp), Arrays.toString(got));
+    }
+
+    public static int gcd(int m, int n) {
+        return n == 0 ? m : gcd(n, m % n);
+    }
+
+    public static boolean isCoprime(int m, int n) {
+        return gcd(m, n) == 1;
+    }
+
+    public static boolean isPerfectTotient(int n) {
+        int i = n;
+        int s = 0;
+        while (i >= 1) {
+            ArrayList<Integer> coprimes = new ArrayList<Integer>();
+            for (int j = 1; j < i; j++) {
+                if (isCoprime(j, i)) {
+                    coprimes.add(j);
+                }
+            }
+            i = coprimes.size();
+            s = s + i;
+        }
+
+        return n == s;
+    }
+
+    public static Integer[] firstPerfectTotient(int n) {
+        ArrayList<Integer> fpt = new ArrayList<Integer>();
+
+        int i  = 1;
+        while (fpt.size() < n) {
+            if (isPerfectTotient(i)) {
+                fpt.add(i);
+            }
+            i++;
+        }
+
+        return fpt.toArray(new Integer[fpt.size()]);
+    }
+}