Catalan number

Catalan.java

public class CatalanNumber {
	
	public static void main( String[] args ){
		System.out.println( countTrees( 17) );
	}
	static long countTrees(int numkeys){
		if(numkeys>1){
		    long sum=0;

		    for(int i= 1; i <=numkeys; i++){
		    	long lcount = countTrees(i-1);
		    	long rcount = countTrees(numkeys-i);
		        sum += lcount*rcount;
		    }
		    return(sum);
		}else
		    return(1);
		}
}