public class MotzkinNumber {

	public static void main(String[] args) {
		for(int i=0;i<=20;i++)System.out.format("%d:%d%n",i,M(i));

	}
	public static int M(int n) {
		if(n==0 || n==1)
			return 1;
		int temp = 0;
		for(int i = 0;i<=n-2;i++)temp+=M(i)*M(n-2-i);
		return M(n-1)+temp;
	}

}