public static void main(String args[]){
        CountNumberOfTreesInBST cnt = new CountNumberOfTreesInBST();
        System.out.println(cnt.countTrees(3));
        System.out.println(cnt.countTrees(4));
    }
http://www.geeksforgeeks.org/program-nth-catalan-number/
Count number of binary search tree created for array of size n
src/com/interview/dynamic/CountNumberOfTreesInBST.java