Implement Lab 6 Exercise 6 (number triangle)

I spotted a neat way of doing this before I had to head off so couldn't resist

week1.java

@@ -250,6 +250,7 @@ class Lab6 extends Lab {
         System.out.println(String.format("%n"));
         new six3();
         new six5();
+        new six6();
     }
 
     /**
@@ -286,6 +287,39 @@ class Lab6 extends Lab {
             System.out.println(String.format("TODO / NOT IMPLEMENTED until we get stdin working"));
         }
     }
+    /**
+     * Produce a number triangle
+     *
+     * eg:
+     *    1
+     *   2 2
+     *  3 3 3
+     * 4 4 4 4
+     */
+    class six6 extends Section {
+        public six6() {
+            super(6);
+            numberTriangle(8);
+        }
+    }
+
+    /**
+     * @param num Size of triangle
+     */
+    public void numberTriangle(int num) {
+        /* Observations:
+           - for even-sized triangles, preceding number of spaces starts at n=rows and decrements
+           - for even-sized triangles even numbers have odd spaces and vice versa
+        */
+        int spaces = num;
+        for (int i = 1; i <= num; i++) {
+            System.out.println(" ".repeat(spaces)
+                               + String.format("%s ", i).repeat(i)
+                               + " ".repeat(spaces-1)
+                               );
+            spaces--;
+        }
+    }
 
     public void writeTimesTable(int num, int limit) {
         for (int i = 0; i < (limit + 1); i++) {