# Find Nth term of the series 1, 6, 18, 40, 75, ….

Given a number n, the task is to find the n-th term in series 1, 6, 18, 40, 75, …

Example:

```Input: N = 2
Output: 6
Explanation:
2nd term = (2^2*(2+1))/2
= 6

Input: N = 5
Output: 75
Explanation:
5th term = (5^2*(5+1))/2
= 75
```

Approach:

Nth term = (N^2*(N+1))/2

Implementation of the above approach is given below:

## C++

 `// CPP code to generate ` `// 'Nth' term of this sequence ` ` `  `#include ` `using` `namespace` `std; ` ` `  `// Function to generate a fixed number ` `int` `nthTerm(``int` `N) ` `{ ` `    ``int` `nth = 0; ` ` `  `    ``//(N^2*(N+1))/2 ` `    ``nth = (N * N * (N + 1)) / 2; ` ` `  `    ``return` `nth; ` `} ` ` `  `// Driver Method ` `int` `main() ` `{ ` `    ``int` `N = 5; ` ` `  `    ``cout << nthTerm(N) << endl; ` ` `  `    ``return` `0; ` `} `

## Java

 `// Java code to generate ` `// 'Nth' term of this sequence ` ` `  `class` `GFG { ` ` `  `    ``// Function to generate a fixed number ` `    ``public` `static` `int` `nthTerm(``int` `N) ` `    ``{ ` `        ``int` `nth = ``0``; ` ` `  `        ``//(N^2*(N+1))/2 ` `        ``nth = (N * N * (N + ``1``)) / ``2``; ` ` `  `        ``return` `nth; ` `    ``} ` ` `  `    ``// Driver Method ` `    ``public` `static` `void` `main(String[] args) ` `    ``{ ` `        ``int` `N = ``5``; ` ` `  `        ``System.out.println(nthTerm(N)); ` `    ``} ` `    ``// This code is contributed by 29AjayKumar ` `} `

## Python3

 `# python program to find out'Nth' term of this sequence  ` ` `  `# Function to generate a fixed number ` `def` `nthTerm(N): ` `    ``nth ``=` `0` `    ``nth ``=` `(N ``*` `N ``*` `(N ``+` `1``))``/``/``2` `    ``return` `nth ` ` `  `# Driver code ` `N ``=` `5` `print``(nthTerm(N)) ` ` `  `# This code is contributed by Shrikant13 `

## C#

 `// C# code to generate ` `// 'Nth' term of this sequence ` ` `  `using` `System; ` `public` `class` `GFG { ` ` `  `    ``// Function to generate a fixed number ` `    ``public` `static` `int` `nthTerm(``int` `N) ` `    ``{ ` `        ``int` `nth = 0; ` ` `  `        ``//(N^2*(N+1))/2 ` `        ``nth = (N * N * (N + 1)) / 2; ` ` `  `        ``return` `nth; ` `    ``} ` ` `  `    ``// Driver Method ` `    ``public` `static` `void` `Main(``string``[] args) ` `    ``{ ` `        ``int` `N = 5; ` ` `  `        ``Console.WriteLine(nthTerm(N)); ` `    ``} ` `} ` ` `  `// This code is contributed by Shrikant13 `

## PHP

 ` `

Output:

```75
```

Time Complexity: O(1)

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