Given a number N, the task is to find the sum of first N number of series:
-1, 2, 11, 26, 47, 74, …..
Examples:
Input: N = 3 Output: 12 Explanation: Sum = (N * (N + 1) * (2 * N - 5) + 4 * N) / 2 = (3 * (3 + 1) * (2 * 3 - 5) + 4 * 3) / 2 = 12 Input: N = 9 Output: 603
Approach:
The Nth term of the given series can be generalised as:
Nth term of the series
Below is the implementation of the above approach:
C++
// CPP program to find SUM // upto N-th term of the series: // -1, 2, 11, 26, 47, 74, ..... #include <iostream> using namespace std;
// calculate Nth term of series int findSum( int N)
{ return (N * (N + 1) * (2 * N - 5) + 4 * N) / 2;
} // Driver Function int main()
{ // Get the value of N
int N = 3;
// Get the sum of the series
cout << findSum(N) << endl;
return 0;
} |
Java
// Java program to find SUM // upto N-th term of the series: // -1, 2, 11, 26, 47, 74, ..... import java.util.*;
class solution
{ static int findSum( int N)
{ return (N * (N + 1 ) * ( 2 * N - 5 ) + 4 * N) / 2 ;
} //driver function public static void main(String arr[])
{ // Get the value of N
int N = 3 ;
// Get the sum of the series
System.out.println(findSum(N));
} } //THis code is contributed by //Surendra_Gangwar |
Python3
# Python3 program to find sum # upto N-th term of the series: # -1, 2, 11, 26, 47, 74, ..... # calculate Nth term of series def findSum(N):
return ((N * (N + 1 ) *
( 2 * N - 5 ) + 4 * N) / 2 )
#Driver Function if __name__ = = '__main__' :
#Get the value of N
N = 3
#Get the sum of the series
print (findSum(N))
#this code is contributed by Shashank_Sharma |
C#
// C# program to find SUM // upto N-th term of the series: // -1, 2, 11, 26, 47, 74, ..... using System;
class GFG
{ static int findSum( int N)
{ return (N * (N + 1) *
(2 * N - 5) + 4 * N) / 2;
} // Driver Code static public void Main ()
{ // Get the value of N
int N = 3;
// Get the sum of the series
Console.Write(findSum(N));
} } // This code is contributed by Raj |
PHP
<?php // PHP program to find SUM // upto N-th term of the series: // -1, 2, 11, 26, 47, 74, ..... // calculate Nth term of series function findSum( $N )
{ return ( $N * ( $N + 1) *
(2 * $N - 5) + 4 * $N ) / 2;
} // Driver Code // Get the value of N $N = 3;
// Get the sum of the series echo findSum( $N ) . "\n" ;
// This code is contributed // by Akanksha Rai(Abby_akku) ?> |
Javascript
<script> // javascript program to find SUM // upto N-th term of the series: // -1, 2, 11, 26, 47, 74, ..... function findSum(N)
{ return (N * (N + 1) * (2 * N - 5) + 4 * N) / 2;
} //driver function // Get the value of N
var N = 3;
// Get the sum of the series
document.write(findSum(N));
// This code is contributed by 29AjayKumar </script> |
Output:
12
Time Complexity: O(1)
Auxiliary Space: O(1)