java

public class  {
    public static void main(String[] args) {
        long sum = 0;   
        
        for (int i=1; i<=20; i++) {
            sum += fun(i);
        }

        System.out.println("1到20的阶乘为："+sum);
    }

    private static long fun(int i) {
        long temp = 1;
        for (int j=1; j<=i; j++) {
            temp *= j;
        }

        return temp;
    }
}