# Find the sum of N terms of the series 1, (2+3), (4+5+6), …..

• Last Updated : 14 Feb, 2022

Given a positive integer, N. Find the sum of the first N term of the series-

1, (2+3), (4+5+6),….,till N terms

Examples:

Input: N = 5

Output: 120

Input: N = 1

Output: 1

Approach: The sequence is formed by using the following pattern. For any value N-

SN = N * (N + 1) * (N2 + N + 2) / 8

Below is the implementation of the above approach:

## C++

 `// C++ program to implement``// the above approach` `#include ``using` `namespace` `std;` `// Function to return sum of``// N term of the series` `int` `findSum(``int` `N)``{` `    ``return` `N``      ``* (N + 1)``      ``* (N * N + N + 2) / 8;``}` `// Driver Code``int` `main()``{``    ``int` `N = 5;` `    ``cout << findSum(N);``}`

## Java

 `/*package whatever //do not write package name here */` `import` `java.io.*;` `class` `GFG {` `    ``// Function to return sum of``    ``// N term of the series``    ``static` `int` `findSum(``int` `N)``    ``{` `        ``return` `N * (N + ``1``) * (N * N + N + ``2``) / ``8``;``    ``}` `    ``// Driver Code``    ``public` `static` `void` `main(String[] args)``    ``{``        ``int` `N = ``5``;` `        ``System.out.println(findSum(N));``    ``}``}` `// This code is contributed by Potta Lokesh`

## Python3

 `# Python 3 program for the above approach` `# Function to return sum of``# N term of the series` `def` `findSum(N):``    ``return` `N ``*` `(N ``+` `1``) ``*` `(N ``*` `N ``+` `N ``+` `2``) ``/``/` `8`  `# Driver Code``if` `__name__ ``=``=` `"__main__"``:``  ` `    ``# Value of N``    ``N ``=` `5``    ``print``(findSum(N))` `# This code is contributed by Abhishek Thakur.`

## C#

 `/*package whatever //do not write package name here */``using` `System;` `class` `GFG``{` `  ``// Function to return sum of``  ``// N term of the series``  ``static` `int` `findSum(``int` `N)``  ``{` `    ``return` `N * (N + 1) * (N * N + N + 2) / 8;``  ``}` `  ``// Driver Code``  ``public` `static` `void` `Main()``  ``{``    ``int` `N = 5;` `    ``Console.Write(findSum(N));``  ``}``}` `// This code is contributed by Saurabh Jaiswal`

## Javascript

 `// Javascript program to implement``// the above approach` `// Function to return sum of``// N term of the series``function` `findSum(N)``{` `    ``return` `N``      ``* (N + 1)``      ``* (N * N + N + 2) / 8;``}` `// Driver Code``let N = 5``document.write(findSum(N))` `// This code is contributed by saurabh_jaiswal.`

Output

`120`

Time Complexity: O(1)
Auxiliary Space: O(1)

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