Change project structure to a Maven Java project + Refactor (#2816)

src/main/java/com/thealgorithms/maths/LeonardoNumber.java

@@ -0,0 +1,21 @@
+package com.thealgorithms.maths;
+
+public class LeonardoNumber {
+
+    public static int leonardoNumber(int n) {
+        if (n < 0) {
+            return 0;
+        }
+        if (n == 0 || n == 1) {
+            return 1;
+        }
+        return (leonardoNumber(n - 1) + leonardoNumber(n - 2) + 1);
+    }
+
+    public static void main(String args[]) {
+        for (int i = 0; i < 20; i++) {
+            System.out.print(leonardoNumber(i) + " ");
+        }
+
+    }
+}