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March 3rd, 2017, 05:50 AM   #1
Joined: Dec 2016
From: Netherlands

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java programming incorrect answer

i have to write a program that gives the summation of 1/i for any given i. i came up with the following program but for some reason it always provides the answer 1.0, can someone tell me what is wrong here?

import java.util.Scanner;
class Series{
Scanner sc = new Scanner(;
double series(int i){
if (i==1)
return 1;
return 1/(i*i) + series(i-1);
public void demo(){
int i;
System.out.println("Provide a number to compute the series for");
i = sc.nextInt();
System.out.println("series of " + i + " is " + series(i));
public static void main(String[] args) {
new Series().demo();
MathAboveMeth is offline  
March 3rd, 2017, 06:33 AM   #2
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From: Ottawa Ontario, Canada

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Originally Posted by MathAboveMeth View Post
i have to write a program that gives the summation of 1/i for any given i.
If i = 2, what d'hell is "summed"?
Please provide an example.
Your post is "obscure"...or do I need another coffee?
Denis is offline  
March 3rd, 2017, 06:53 AM   #3
Xxmarijnw's Avatar
Joined: Feb 2017
From: Netherlands

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Math Focus: Trigonometry and complex numbers
Assuming $\displaystyle i$ is a variable and not the imaginary unit:

$\displaystyle \sum_{i=0}^\infty \frac{\alpha}i = \infty \thinspace \text{if} \thinspace \alpha\ne{0} \thinspace \wedge \thinspace i\ne{0}$

This can be proven with the harmonic series test. So what do you mean exactly? If you mean just $\displaystyle \frac{1}i$ you can use $\displaystyle i^{-1}$
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March 3rd, 2017, 09:25 AM   #4
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Joined: Jul 2010
From: St. Augustine, FL., U.S.A.'s oldest city

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Math Focus: Calculus/ODEs
I believe the OP's program is supposed to find:

$\displaystyle S_i=\sum_{k=1}^{i}\left(\frac{1}{k}\right)$

It looks to me though, the algorithm coded would provide:

$\displaystyle S_i=\sum_{k=1}^{i}\left(\frac{1}{k^2}\right)$

However, I'm not a Java programmer.
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March 3rd, 2017, 09:46 AM   #5
Joined: Jan 2016
From: Athens, OH

Posts: 93
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Your only error is in method series. You said i is an int, so 1/i*i is 0 for any i>1! So just change 1/i*i to 1.0/i*i.

By the way I am surprised that your program runs as given. I thought main had to be within a public class?
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