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Program to print the sum of the given nth term

  • Last Updated : 09 Aug, 2021
Geek Week

Given the value of the n. You have to find the sum of the series where the nth term of the sequence is given by:
Tn = n2 – ( n – 1 )2
Examples : 

Input : 3
Output : 9

Explanation: So here the term of the sequence upto n = 3 are: 
             1, 3, 5 And hence the required sum is = 1 + 3 + 5 = 9

Input : 6
Output : 36

Simple Approach 
Just use a loop and calculate the sum of each term and print the sum. 

C++




// CPP program to find summation of series
#include <bits/stdc++.h>
using namespace std;
 
int summingSeries(long n)
{
    // use of loop to calculate
    // sum of each term
    int S = 0;
    for (int i = 1; i <= n; i++)
        S += i * i - (i - 1) * (i - 1);
     
    return S;
}
 
// Driver Code
int main()
{
    int n = 100;
    cout << "The sum of n term is: "
        << summingSeries(n) << endl;
    return 0;
}

Java




// JAVA program to find summation of series
import java.io.*;
import java.math.*;
import java.text.*;
import java.util.*;
import java.util.regex.*;
 
class GFG
{
 
    // function to calculate sum of series
    static int summingSeries(long n)
    {
        // use of loop to calculate
        // sum of each term
        int S = 0;
        for (i = 1; i <= n; i++)
            S += i * i - (i - 1) * (i - 1);    
         
        return S;
    }
 
    // Driver code
    public static void main(String[] args)
    {
        int n = 100;
        System.out.println("The sum of n term is: " +
                            summingSeries(n));
    }
}

Python3




# Python3 program to find summation
# of series
 
def summingSeries(n):
 
    # use of loop to calculate
    # sum of each term
    S = 0
    for i in range(1, n+1):
        S += i * i - (i - 1) * (i - 1)
     
    return S
 
# Driver Code
n = 100
print("The sum of n term is: ",
           summingSeries(n), sep = "")
# This code is contributed by Smitha.

C#




// C# program to illustrate...
// Summation of series
using System;
 
class GFG
{
 
    // function to calculate sum of series
    static int summingSeries(long n)
    {
 
        // Using the pow function calculate
        // the sum of the series
        return (int)Math.Pow(n, 2);
    }
 
    // Driver code
    public static void Main(String[] args)
    {
        int n = 100;
        Console.Write("The sum of n term is: " +
                        summingSeries(n));
    }
}
 
// This code contribute by Parashar...

PHP




<?php
// PHP program to find
// summation of series
 
function summingSeries( $n)
{
     
    // use of loop to calculate
    // sum of each term
    $S = 0;
    for ($i = 1; $i <= $n; $i++)
         $S += $i * $i - ($i - 1) *
                       ($i - 1);
     
    return $S;
}
 
// Driver Code
$n = 100;
echo "The sum of n term is: ",
summingSeries($n) ;
 
// This code contribute by vt_m.
?>

Javascript




<script>
// Javascript program to find summation of series
 
function summingSeries(n)
{
    // use of loop to calculate
    // sum of each term
    let S = 0;
    for (let i = 1; i <= n; i++)
        S += i * i - (i - 1) * (i - 1);
     
    return S;
}
 
// Driver Code
let n = 100;
document.write("The sum of n term is: " + summingSeries(n));
 
// This code is contributed by rishavmahato348.
</script>

Output: 

The sum of n term is: 10000

Time complexity – O(N) 
Space complexity – O(1)
Efficient Approach 
Use of mathematical approach can solve this problem in more efficient way.
 

Tn = n2 – (n-1)2
Sum of the series is given by (S) = SUM( Tn )
LET US TAKE A EXAMPLE IF 
N = 4 
It means there should be 4 terms in the series so
1st term = 12 – ( 1 – 1 )2 
2nd term = 22 – ( 2 – 1 )2 
3th term = 32 – ( 3 – 1 )2 
4th term = 42 – ( 3 – 1 )2
SO SUM IS GIVEN BY = (1 – 0) + (4 – 1) + (9 – 4) + (16 – 9) 
= 16
FROM THIS WE HAVE NOTICE THAT 1, 4, 9 GET CANCELLED FROM THE SERIES 
ONLY 16 IS LEFT WHICH IS EQUAL TO THE SQUARE OF N
So from the above series we notice that each term gets canceled from the next term, only the last term is left which is equal to N2.
 



C++




// CPP program to illustrate...
// Summation of series
 
#include <bits/stdc++.h>
using namespace std;
 
int summingSeries(long n)
{
    // Sum of n terms is n^2
    return pow(n, 2);
}
 
// Driver Code
int main()
{
    int n = 100;
    cout << "The sum of n term is: "
         << summingSeries(n) << endl;
    return 0;
}

Java




// JAVA program to illustrate...
// Summation of series
 
import java.io.*;
import java.math.*;
import java.text.*;
import java.util.*;
import java.util.regex.*;
 
class GFG
{
 
    // function to calculate sum of series
    static int summingSeries(long n)
    {
 
        // Using the pow function calculate
        // the sum of the series
        return (int)Math.pow(n, 2);
    }
 
    // Driver code
    public static void main(String[] args)
    {
        int n = 100;
        System.out.println("The sum of n term is: " +
                            summingSeries(n));
    }
}

Python3




# Python3 program to illustrate...
# Summation of series
import math
 
def summingSeries(n):
 
    # Sum of n terms is  n^2
    return math.pow(n, 2)
 
# Driver Code
n = 100
print ("The sum of n term is: ",
        summingSeries(n))
# This code is contributed by mits.

C#




// C# program to illustrate...
// Summation of series
using System;
 
class GFG
{
    // function to calculate sum of series
    static int summingSeries(long n)
    {
        // Using the pow function calculate
        // the sum of the series
        return (int)Math.Pow(n, 2);
    }
 
    // Driver code
    public static void Main()
    {
        int n = 100;
           Console.Write("The sum of n term is: " +
                              summingSeries(n));
    }
}
 
// This code is contributed by nitin mittal.

PHP




<?php
// PHP program to illustrate...
// Summation of series
 
function summingSeries($n)
{
    // Sum of n terms is  n^2
    return pow($n, 2);
}
 
// Driver Code
$n = 100;
echo "The sum of n term is: ",
summingSeries($n);
 
// This code contribute by vt_m.
?>

Javascript




<script>
// Javascript program to illustrate...
// Summation of series
 
function summingSeries(n)
{
    // Sum of n terms is n^2
    return Math.pow(n, 2);
}
 
// Driver Code
let n = 100;
document.write("The sum of n term is: "
    + summingSeries(n) + "<br>");
     
    // This code is contributed by subham348.
</script>

Output: 

The sum of n term is: 10000

Time complexity – O(1) 
Space complexity – O(1) 
 

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