public static int utopianTree(int n) {
        int closestOdd = n % 2 == 0 ? n + 1: n;
        int i = ((closestOdd-1)/2) + 2;
        int res = (int)Math.pow(2, i) - 2;
        
        if(n%2 == 0) {
            res /= 2;
        }
        
        return res;
    }