编程题21 求阶数总和

题目：求1+2!+3!+…+20!的和

 

 

public int sum(){
   int sum=0;
   for(int i=1;i<=20;i++){
       sum+=factorials（i）;
   }
   return sum;
}
public static int factorials(int n){
   int multiple=1;
   for(int i=1;i<=n;i++){
       multiple*=i;
   }
   return multiple;
}