Java - Sumatoria factoriales impares

public class Util {

	private Util() {}

	public static long factorial(int n) {

		if(0 > n) {

			throw new IllegalArgumentException("n necesita ser mayor o igual a cero.");

		}

		long result = 1l;

		for(int k = 2 ; k <=n ; k ++) {

			result *= k;

		}

		return result;

	}

	public static long sum(int n) {

		long sum = 0l;

		for(int i = 0 ; i < n ; i++) {

			 sum += factorial(2*i+1);

		}

		return sum;

	}

}

import java.util.Scanner;

public class Test {

	public static void main(String[] args) {

		Scanner lea = null;

		int n;

		try {

			lea = new Scanner(System.in);

			do {

				System.out.print("Introduzca un número: ");

				n = lea.nextInt();

			} while (!(n > 0));

			System.out.println("La sumatoria es  :     " + Util.sum(n));

		} finally {

			if (null != lea) {

				lea.close();

			}

		}

	}

}