十进制数

给您一个数字n，任务是找到第n个十进制数。十进制数是将三角形和正方形数的概念扩展到十进制(十边形多边形)的图形数。第n个十进制数计算n个嵌套的十进制图案中的点数，它们全部共享一个公共角，其中该模式中的第i个十进制具有由i个点组成的边，这些点相互间隔一个单位。

例子：

Input : n = 3
Output : 27

Input : n = 7
Output : 175
 

第n个十进制数由以下公式给出
(4n ² – 3n) 。

C++

// C++ program to find nth decagonal number
#include 
using namespace std;
  
// Function to calculate decagonal number
int decagonal(int n)
{
    // Formula for finding nth decagonal number
    return 4 * n * n - 3 * n;
}
  
// Driver function
int main()
{
    int n = 10;
    cout << n << "th decagonal number :" << decagonal(n);
    return 0;
}

Java

// JAVA Code for Decagonal Numbers
import java.util.*;
 
class GFG {
 
    // Function to calculate
    // decagonal number
    static int decagonal(int n)
    {
        // Formula for finding nth
        // decagonal number
        return 4 * n * n - 3 * n;
    }
     
    /* Driver function */
    public static void main(String[] args)
    {   
        int n = 10;
        System.out.println(n + "th decagonal number :"
                            + decagonal(n));
    }
}
 
// This code is contributed by Arnav Kr. Mandal.

Python

# Python program to find nth decagonal number
def decagonal(n):
    return 4 * n * n - 3 * n
  
# Driver code
n = 10
print(n, "th decagonal number :", decagonal(n))

C#

// C# Code for Decagonal Numbers
using System;
 
class GFG {
 
    // Function to calculate
    // decagonal number
    static int decagonal(int n)
    {
        // Formula for finding nth
        // decagonal number
        return 4 * n * n - 3 * n;
    }
     
    // Driver Code
    public static void Main()
    {
        int n = 10;
        Console.Write(n + "th decagonal number : "
                                   + decagonal(n));
    }
}
 
// This code is contributed by vt_m.

Javascript

 
// JavaScript program for Decagonal Numbers
 
// Function to calculate
// decagonal number
function decagonal(n)
{
     
    // Formula for finding nth
    // decagonal number
    return 4 * n * n - 3 * n;
}
 
// Driver code
let n = 10;
document.write(n + "th decagonal number : " +
               decagonal(n));
                
// This code is contributed by souravghosh0416
 

输出：

10th decagonal number : 370