The answer is not coming correct

#1

I am applying the formula
Cn = (2*(2*n - 1) / (n+1) ) * Cn-1
so is this corect or …?

#2

import java.util.; public class Main { public static long helper(long n){ if(n == 0){ return 1; } long first = 2(2*n - 1); long second = n + 1; return (first/second)*helper(n-1); } public static void main(String args[]) { Scanner s = new Scanner(System.in); long n = s.nextInt(); System.out.println(helper(n)); } }

#3
#4

the formula for nth catalyn number is

thus your code would be :-

class CatalnNumber { 

// A recursive function to find nth catalan number 

int catalan(int n) { 
	int res = 0; 
	
	// Base case 
	if (n <= 1) { 
		return 1; 
	} 
	for (int i = 0; i < n; i++) { 
		res += catalan(i) * catalan(n - i - 1); 
	} 
	return res; 
} 

public static void main(String[] args) { 
	CatalnNumber cn = new CatalnNumber(); 
	for (int i = 0; i < 10; i++) { 
		System.out.print(cn.catalan(i) + " "); 
	} 
}

}

you can optimize it using dp