用Java写一个1阶乘到20阶乘之和的代码并且输出答案

public class FactorialSum {
    public static void main(String[] args) {
        long sum = 0;
        long factorial = 1;
        for (int i = 1; i <= 20; i++) {
            factorial *= i;
            sum += factorial;
        }
        System.out.println("1! + 2! + 3! + ... + 20! = " + sum);
    }
}

输出结果为：

1! + 2! + 3! + ... + 20! = 2561327494111820313