public class Test{
public long factorial(int number){
if(number == 1 ){
return number;
}
return number*factorial(number-1);//想象是20*19*18*17*…… 直到乘1返回
}
public static void main(String[] args) {
Test t = new Test();
long sum = 0;
for(int i=0;i<20;i++){
sum += t.factorial(i+1);//阶乘相加
}
System.out.println(sum);
}
}
