help with basic sum calculator in java

Ok so I am trying to make a sum calculator that calculates the following:

∑ 2n+1

In this problem the user inputs the upper limit of the program and the lower limit is always 0.

This is what I got:

import java.io.*;

public class sum

{

public static void main(String args[]) throws IOException

{

BufferedReader keybd = new BufferedReader(new InputStreamReader(System.in));

int n;

System.out.print("Input the upper limit: ");

n = Integer.parseInt(keybd.readLine());

int calc=2*n+1;

for (int i=0; i<=n; i++)

{

calc=calc+i;

}

System.out.println(calc);

}

}

The program works (sort of). When I do test runs it gives me wrong answers, when n >= 2. When I input 0 or 1 for upper limit it gives me correct answer, but when the upper limit is greater than or equal to 2, the answer is wrong.

For instance when I run the program and input 2 for the upper limit, the answer it gives me is 8 ...

but when i do the sum by hand the correct answer is 9:

[2(0)+1] + [2(1)+1] + [2(2)+1]

= 1 + 3 + 5

= 9

This problem has been bugging me for several hours. Any help appreciated thanks! :)