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Second decagonal numbers
• Last Updated : 06 Apr, 2021

The Second decagonal numbers series can be represented as

7, 22, 45, 76, 115, 162, 217, 280,,…..

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

Input: N = 1
Output: 7

Input: N = 4
Output: 76

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

1st Term = 1 * (4*1 + 3) = 7
2nd term = 2 * (4*2 + 3) = 22
3rd term = 3 * (4*3 + 3) = 45
4th term = 4 * (4*4 + 3) = 76

Nth term = n * (4 * n + 3)
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 ``#include ``using` `namespace` `std;` `// Function to find N-th term``// in the series``void` `findNthTerm(``int` `n)``{``    ``cout << n * (4 * n + 3) << endl;``}` `// Driver Code``int` `main()``{``    ``int` `N = 4;``    ``findNthTerm(N);` `    ``return` `0;``}`

## Java

 `// Java program for the above approach``class` `GFG{` `// Function to find N-th term``// in the series``static` `void` `findNthTerm(``int` `n)``{``    ``System.out.println(n * (``4` `* n + ``3``));``}` `// Driver code``public` `static` `void` `main(String[] args)``{``    ``int` `N = ``4``;``    ` `    ``findNthTerm(N);``}``}` `// This code is contributed by Pratima Pandey`

## Python3

 `# Python3 implementation to``# find N-th term in the series` `# Function to find N-th term``# in the series``def` `findNthTerm(n):` `    ``print``(n ``*` `(``4` `*` `n ``+` `3``))` `# Driver Code``N ``=` `4``;``findNthTerm(N);` `# This code is contributed by Code_Mech`

## C#

 `// C# program for the above approach``using` `System;``class` `GFG{` `// Function to find N-th term``// in the series``static` `void` `findNthTerm(``int` `n)``{``    ``Console.WriteLine(n * (4 * n + 3));``}` `// Driver code``public` `static` `void` `Main(String[] args)``{``    ``int` `N = 4;``    ` `    ``findNthTerm(N);``}``}` `// This code is contributed by 29AjayKumar`

## Javascript

 ``
Output:
`76`

Time Complexity: O(1)

Auxiliary Space: O(1)

Reference: OEIS

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