Given a number n, the task is to find the nth term of the series

1, 4, 15, 24, 45, 60, 91, 112, 153…..

where 0 < n < 100000000.**Examples:**

Input:n = 10Output:180Input:n = 5Output:45

**Approach:**

The idea is very simple but hard to recognise.

If n is odd, the nth term will be [ ( 2 * ( n^2 ) ) – n ].

If n is even, the nth term will be [ 2 * ( (n^2) – n ) ].

**Implementation:**

## C++

`#include <stdio.h>` `// function to calculate nth term of the series` `long` `long` `int` `nthTerm(` `long` `long` `int` `n)` `{` ` ` `// variable nth will store the nth term of series` ` ` `long` `long` `int` `nth;` ` ` `// if n is even` ` ` `if` `(n % 2 == 0)` ` ` `nth = 2 * ((n * n) - n);` ` ` `// if n is odd` ` ` `else` ` ` `nth = (2 * n * n) - n;` ` ` `// return nth term` ` ` `return` `nth;` `}` `// Driver code` `int` `main()` `{` ` ` `long` `long` `int` `n;` ` ` `n = 5;` ` ` `printf` `(` `"%lld\n"` `, nthTerm(n));` ` ` `n = 25;` ` ` `printf` `(` `"%lld\n"` `, nthTerm(n));` ` ` `n = 25000000;` ` ` `printf` `(` `"%lld\n"` `, nthTerm(n));` ` ` `n = 250000007;` ` ` `printf` `(` `"%lld\n"` `, nthTerm(n));` ` ` `return` `0;` `}` |

## Java

`// Java implementation of the above approach` `class` `GFG` `{` ` ` `// function to calculate nth` ` ` `// term of the series` ` ` `static` `long` `nthTerm(` `long` `n)` ` ` `{` ` ` `// variable nth will store the` ` ` `// nth term of series` ` ` `long` `nth;` ` ` ` ` `// if n is even` ` ` `if` `(n % ` `2` `== ` `0` `)` ` ` `nth = ` `2` `* ((n * n) - n);` ` ` ` ` `// if n is odd` ` ` `else` ` ` `nth = (` `2` `* n * n) - n;` ` ` ` ` `// return nth term` ` ` `return` `nth;` ` ` `}` ` ` ` ` `// Driver code` ` ` `public` `static` `void` `main(String []args)` ` ` `{` ` ` `long` `n;` ` ` `n = ` `5` `;` ` ` `System.out.println(nthTerm(n));` ` ` ` ` `n = ` `25` `;` ` ` `System.out.println(nthTerm(n));` ` ` ` ` `n = ` `25000000` `;` ` ` `System.out.println(nthTerm(n));` ` ` ` ` `n = ` `250000007` `;` ` ` `System.out.println(nthTerm(n));` ` ` `}` `}` `// This code is contributed by Ryuga` |

## Python3

`# function to calculate nth term of the series` `def` `nthTerm(n):` ` ` `# variable nth will store the nth` ` ` `# term of series` ` ` `nth ` `=` `0` ` ` `# if n is even` ` ` `if` `(n ` `%` `2` `=` `=` `0` `):` ` ` `nth ` `=` `2` `*` `((n ` `*` `n) ` `-` `n)` ` ` `# if n is odd` ` ` `else` `:` ` ` `nth ` `=` `(` `2` `*` `n ` `*` `n) ` `-` `n` ` ` `# return nth term` ` ` `return` `nth` `# Driver code` `n ` `=` `5` `print` `(nthTerm(n))` `n ` `=` `25` `print` `(nthTerm(n))` `n ` `=` `25000000` `print` `(nthTerm(n))` `n ` `=` `250000007` `print` `(nthTerm(n))` `# This code is contributed by` `# Mohit kumar 29` |

## C#

`// C# implementation of the above approach` `using` `System;` `class` `GFG` `{` ` ` `// function to calculate nth` ` ` `// term of the series` ` ` `static` `long` `nthTerm(` `long` `n)` ` ` `{` ` ` `// variable nth will store the` ` ` `// nth term of series` ` ` `long` `nth;` ` ` ` ` `// if n is even` ` ` `if` `(n % 2 == 0)` ` ` `nth = 2 * ((n * n) - n);` ` ` ` ` `// if n is odd` ` ` `else` ` ` `nth = (2 * n * n) - n;` ` ` ` ` `// return nth term` ` ` `return` `nth;` ` ` `}` ` ` ` ` `// Driver code` ` ` `public` `static` `void` `Main()` ` ` `{` ` ` `long` `n;` ` ` `n = 5;` ` ` `Console.WriteLine(nthTerm(n));` ` ` ` ` `n = 25;` ` ` `Console.WriteLine(nthTerm(n));` ` ` ` ` `n = 25000000;` ` ` `Console.WriteLine(nthTerm(n));` ` ` ` ` `n = 250000007;` ` ` `Console.WriteLine(nthTerm(n));` ` ` `}` `}` `// This code is contributed by chandan_jnu` |

## PHP

`<?php` `// function to calculate nth term` `// of the series` `function` `nthTerm(` `$n` `)` `{` ` ` `// variable nth will store the` ` ` `// nth term of series` ` ` `$nth` `;` ` ` `// if n is even` ` ` `if` `(` `$n` `% 2 == 0)` ` ` `$nth` `= 2 * ((` `$n` `* ` `$n` `) - ` `$n` `);` ` ` `// if n is odd` ` ` `else` ` ` `$nth` `= (2 * ` `$n` `* ` `$n` `) - ` `$n` `;` ` ` `// return nth term` ` ` `return` `$nth` `;` `}` `// Driver code` `$n` `= 5;` `echo` `nthTerm(` `$n` `), ` `"\n"` `;` `$n` `= 25;` `echo` `nthTerm(` `$n` `), ` `"\n"` `;` `$n` `= 25000000;` `echo` `nthTerm(` `$n` `), ` `"\n"` `;` `$n` `= 250000007;` `echo` `nthTerm(` `$n` `), ` `"\n"` `;` `// This code is contributed by jit_t` `?>` |

## Javascript

`<script>` `// function to calculate nth term of the series` `function` `nthTerm( n)` `{` ` ` `// variable nth will store the nth term of series` ` ` `let nth;` ` ` `// if n is even` ` ` `if` `(n % 2 == 0)` ` ` `nth = 2 * ((n * n) - n);` ` ` `// if n is odd` ` ` `else` ` ` `nth = (2 * n * n) - n;` ` ` `// return nth term` ` ` `return` `nth;` `}` `// Driver code` ` ` `let n = 5;` ` ` `document.write( nthTerm(n) + ` `"<br/>"` `);` ` ` `n = 25;` ` ` `document.write( nthTerm(n) + ` `"<br/>"` `);` ` ` `n = 25000000;` ` ` `document.write( nthTerm(n) + ` `"<br/>"` `);` ` ` `n = 250000007;` ` ` `document.write( nthTerm(n) + ` `"<br/>"` `);` ` ` `// This code contributed by gauravrajput1` `</script>` |

**Output:**

45 1225 1249999950000000 125000006750000091

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