实验2-3-3 求奇数分之一序列前N项和

package com.company;

import java.text.DecimalFormat;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
    // write your code here
        Scanner sc=new Scanner(System.in);
        int N=sc.nextInt();
        double sum=0;
        DecimalFormat df=new DecimalFormat("0.000000");
        for(int i=1;i<=N;i++){
            double id=Double.valueOf(i);
            sum=sum+1/(2*id-1);
        }
        System.out.println("sum = "+df.format(sum));
    }
}