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 <bits/stdc++.h>` `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

`<?php` `// PHP code to generate` `// 'Nth' term of this sequence` `// Function to generate a fixed number` `function` `nthTerm(` `$N` `)` `{` ` ` `$nth` `= 0;` ` ` `// (N^2*(N+1))/2` ` ` `$nth` `= (` `$N` `* ` `$N` `* (` `$N` `+ 1)) / 2;` ` ` `return` `$nth` `;` `}` `// Driver Code` `$N` `= 5;` `echo` `nthTerm(` `$N` `);` `// This code is contributed` `// by chandan_jnu` `?>` |

## Javascript

`<script>` `// Javascript code to generate` `// 'Nth' term of this sequence` `// Function to generate a fixed number` `function` `nthTerm(N)` `{` ` ` `let nth = 0;` ` ` `//(N^2*(N+1))/2` ` ` `nth = parseInt((N * N * (N + 1)) / 2);` ` ` `return` `nth;` `}` `// Driver Method` `let N = 5;` `document.write(nthTerm(N));` `// This code is contributed by subham348.` `</script>` |

**Output:**

75

**Time Complexity:** O(1)

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