Added program to calculate catalan number

CatalanNumbers/NthCalatanNumber.cpp

@@ -0,0 +1,26 @@
+//Program for Nth Catalan number.
+
+#include<iostream>
+using namespace std;
+
+// A recursive function to find nth catalan number
+unsigned long int catalan(unsigned int n)
+{
+    // Base case
+    if (n <= 1) return 1;
+
+    // catalan(n) is sum of catalan(i)*catalan(n-i-1)
+    unsigned long int res = 0;
+    for (int i=0; i<n; i++)
+        res += catalan(i)*catalan(n-i-1);
+
+    return res;
+}
+
+// Driver program to test above function
+int main()
+{
+    for (int i=0; i<10; i++)
+        cout << catalan(i) << " ";
+    return 0;
+}