The **Second heptagonal numbers** series can be represented as

4, 13, 27, 46, 70, 99, 133, 172, 216, …..

Nth term

Given an integer **N**. The task is to find the N-th term of the given series.**Examples**:

Input:N = 1Output:4

Input:N = 4Output:46

**Approach:** The idea is to find the general term for the Second heptagonal numbers. Below is the computation of the general term for second heptagonal numbers:

Series = 4, 13, 27, 46, 70, 99, 133, 172, 216, …..

Difference = 13-4, 27-13, 46-27, 70-46, …………….

Difference = 9, 14, 19, 24……which is a AP

So nth term of given series

nth term = 4 + (9 + 14 + 19 + 24 …… (n-1)terms)

nth term = 4 + (n-1)/2*(2*9+(n-1-1)*5)

nth term = 4 + (n-1)/2*(18+5n-10)

nth term = 4 + (n-1)*(5n+8)/2

nth term = n*(5*n+3)/2

Therefore, the Nth term of the series is given as

Below is the implementation of above approach:

## C++

`// C++ implementation to` `// find N-th term in the series` `#include <iostream>` `#include <math.h>` `using` `namespace` `std;` `// Function to find N-th term` `// in the series` `void` `findNthTerm(` `int` `n)` `{` ` ` `cout << n * (5 * n + 3) / 2` ` ` `<< endl;` `}` `// Driver code` `int` `main()` `{` ` ` `int` `N = 4;` ` ` `findNthTerm(N);` ` ` `return` `0;` `}` |

## Java

`// Java implementation to` `// find N-th term in the series` `class` `GFG{` `// Function to find N-th term` `// in the series` `static` `void` `findNthTerm(` `int` `n)` `{` ` ` `System.out.println(n * (` `5` `* n + ` `3` `) / ` `2` `);` `}` `// Driver code` `public` `static` `void` `main(String[] args)` `{` ` ` `int` `N = ` `4` `;` ` ` ` ` `findNthTerm(N);` `}` `}` `// This code is contributed by Ritik Bansal` |

## Python 3

`# Python implementation to` `# find N-th term in the series` `# Function to find N-th term` `# in the series` `def` `findNthTerm(n):` ` ` `print` `(n ` `*` `(` `5` `*` `n ` `+` `3` `) ` `/` `/` `2` `)` `# Driver code` `N ` `=` `4` `# Function call` `findNthTerm(N)` `# This code is contributed by Vishal Maurya.` |

## C#

`// C# implementation to` `// find N-th term in the series` `using` `System;` `class` `GFG{` `// Function to find N-th term` `// in the series` `static` `void` `findNthTerm(` `int` `n)` `{` ` ` `Console.Write(n * (5 * n + 3) / 2);` `}` `// Driver code` `public` `static` `void` `Main()` `{` ` ` `int` `N = 4;` ` ` ` ` `findNthTerm(N);` `}` `}` `// This code is contributed by Code_Mech` |

## Javascript

`<script>` `// Javascript implementation to` `// find N-th term in the series` `// Function to find N-th term` `// in the series` `function` `findNthTerm(n)` `{` ` ` `document.write(parseInt((n * (5 * n + 3)) / 2));` `}` `// Driver code` `let N = 4;` `findNthTerm(N);` `// This code is contributed by rishavmahato348.` `</script>` |

**Output:**

46

**Time Complexity:** O(1)

**Auxiliary Space:** O(1)

**Reference:**OEIS

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