Program to find the Nth term of series -1, 2, 11, 26, 47……

Given a number N, the task is to find the Nth term of this series:

-1, 2, 11, 26, 47, 74, .....

**Examples:**

Input:3Output:11Explanation:when N = 3 Nth term = ( (3 * N * N) - (6 * N) + 2 ) = ( (3 * 3 * 3) - (6 * 3) + 2 ) = 11Input:9Output:191

**Approach:**

The Nth term of the given series can be generalised as:

Nth term of the series : ( (3 * N * N) - (6 * N) + 2 )

Below is the implementation of the above problem:

**Program:**

## C++

`// CPP program to find N-th term of the series: ` `// 9, 23, 45, 75, 113, 159...... ` ` ` `#include <iostream> ` `using` `namespace` `std; ` ` ` `// calculate Nth term of series ` `int` `nthTerm(` `int` `N) ` `{ ` ` ` `return` `((3 * N * N) - (6 * N) + 2); ` `} ` ` ` `// Driver Function ` `int` `main() ` `{ ` ` ` ` ` `// Get the value of N ` ` ` `int` `N = 3; ` ` ` ` ` `// Find the Nth term ` ` ` `// and print it ` ` ` `cout << nthTerm(N); ` ` ` ` ` `return` `0; ` `} ` |

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## Java

`// Java program to find N-th term of the series: ` `// 9, 23, 45, 75, 113, 159...... ` ` ` `class` `GFG { ` ` ` ` ` `// calculate Nth term of series ` ` ` `static` `int` `nthTerm(` `int` `N) ` ` ` `{ ` ` ` `return` `((` `3` `* N * N) - (` `6` `* N) + ` `2` `); ` ` ` `} ` ` ` ` ` `// Driver code ` ` ` `public` `static` `void` `main(String[] args) { ` ` ` `int` `N = ` `3` `; ` ` ` ` ` `// Find the Nth term ` ` ` `// and print it ` ` ` `System.out.println(nthTerm(N)); ` ` ` `} ` `} ` ` ` `// This code is contributed by bilal-hungund ` |

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## Python3

`# Python3 program to find N-th term ` `# of the series: ` `# 9, 23, 45, 75, 113, 159...... ` ` ` `def` `nthTerm(N): ` ` ` ` ` `#calculate Nth term of series ` ` ` `return` `((` `3` `*` `N ` `*` `N) ` `-` `(` `6` `*` `N) ` `+` `2` `); ` ` ` `# Driver Code ` `if` `__name__` `=` `=` `'__main__'` `: ` ` ` `n ` `=` `3` ` ` ` ` `#Find the Nth term ` ` ` `# and print it ` ` ` `print` `(nthTerm(n)) ` ` ` `# this code is contributed by bilal-hungund ` |

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## C#

`// C# program to find N-th term of the series: ` `// 9, 23, 45, 75, 113, 159...... ` `using` `System; ` `class` `GFG ` `{ ` ` ` `// calculate Nth term of series ` `static` `int` `nthTerm(` `int` `N) ` `{ ` ` ` `return` `((3 * N * N) - (6 * N) + 2); ` `} ` ` ` `// Driver code ` `public` `static` `void` `Main() ` `{ ` ` ` `int` `N = 3; ` ` ` ` ` `// Find the Nth term ` ` ` `// and print it ` ` ` `Console.WriteLine(nthTerm(N)); ` `} ` `} ` ` ` `// This code is contributed by inder_verma ` |

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## PHP

`<?php ` `// PHP program to find N-th term of ` `// the series: 9, 23, 45, 75, 113, 159...... ` ` ` `// calculate Nth term of series ` `function` `nthTerm(` `$N` `) ` `{ ` ` ` `return` `((3 * ` `$N` `* ` `$N` `) - ` ` ` `(6 * ` `$N` `) + 2); ` `} ` ` ` `// Driver Code ` ` ` `// Get the value of N ` `$N` `= 3; ` ` ` `// Find the Nth term ` `// and print it ` `echo` `nthTerm(` `$N` `); ` ` ` `// This code is contributed by Raj ` `?> ` |

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**Output:**

11

**Time Complexity:** O(1)

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