中心十进制数

给定数字n，找到第n个中心十进制数。
居中十进制数是居中的图形编号，它表示一个十进制，其点位于中心，而所有其他点以连续的十进制形式围绕它。来源[Wiki]。

前几个居中十进制数为：
1，11，31，61，101，151，211，281，361，451，551，661…………
例子 ：

Input :  3
Output : 31

Input : 6
Output : 151

在数学中，第n个项的中心十进制数由下式给出：

$Cd_{n}= 5n^2+5n+1$

以下是上述想法的基本实现。

C++

// Program to find nth
// centered decagonal
// number
#include 
using namespace std;
 
// Centered decagonal
// number function
 
int centereddecagonalnum(int n)
{
    // Formula to calculate nth
    // centered decagonal number &
    // return it into main function.
    return (5 * n * n + 5 * n + 1);
}
 
// Driver Code
int main()
{
    int n = 5;
    cout << n << "th centered decagonal"
                          << "number: ";
    cout << centereddecagonalnum(n);
    cout << endl;
    n = 9;
    cout << n << "th centered decagonal"
                          << "number: ";
    cout << centereddecagonalnum(n);
 
    return 0;
}

Java

// Java Program to find nth
// centered decagonal number
import java.io.*;
 
class GFG
{
     
    // Centered decagonal
    // number function
    static int centereddecagonalnum(int n)
    {
         
    // Formula to calculate nth
    // centered decagonal number &
    // return it into main function.
    return (5 * n * n + 5 * n + 1);
    }
 
    // Driver Code
    public static void main (String[] args)
    {
        int n = 5;
        System.out.print(n + "th centered " +
                       "decagonal number: ");
        System.out.println(centereddecagonalnum(n));
 
        n = 9;
        System.out.print(n + "th centered " +
                       "decagonal number: ");
        System.out.println(centereddecagonalnum(n));
    }
}
 
// This code is contributed by m_kit

Python3

# Program to find nth
# centered decagonal number
 
# Centered decagonal
# number function
def centereddecagonalnum(n) :
     
    # Formula to calculate
    # nth centered decagonal
    # number & return it
    # into main function.
    return (5 * n * n +
            5 * n + 1)
 
# Driver Code
if __name__ == '__main__' :
         
    n = 5
    print(n,"th centered decagonal " +
                          "number : ",
              centereddecagonalnum(n))
 
    n = 9
    print(n,"th centered decagonal " +
                          "number : ",
              centereddecagonalnum(n))
               
# This code is contributed by m_kit

C#

// Program to find nth
// centered decagonal
// number
using System;
 
class GFG
{
// Centered decagonal
// number function
static int centereddecagonalnum(int n)
{
    // Formula to calculate nth
    // centered decagonal number &
    // return it into main function.
    return (5 * n * n + 5 * n + 1);
}
 
// Driver Code
static public void Main ()
{
int n = 5;
Console.Write(n + "th centered decagonal"+
                              "number: ");
Console.WriteLine(centereddecagonalnum(n));
 
n = 9;
Console.Write(n + "th centered decagonal"+
                              "number: ");
Console.WriteLine(centereddecagonalnum(n));
}
}
 
// This code is contributed by aj_36

Javascript

 
// Javascript Program to find nth
// centered decagonal number
 
// Centered decagonal
// number function
function centereddecagonalnum(n)
{
     
    // Formula to calculate nth
    // centered decagonal number &
    // return it into main function.
    return (5 * n * n + 5 * n + 1);
}
 
// Driver Code
var n = 5;
document.write(n + "th centered " +
               "decagonal number: ");
document.write(centereddecagonalnum(n) + "<br>");
 
n = 9;
document.write(n + "th centered " +
               "decagonal number: ");
document.write(centereddecagonalnum(n));
 
// This code is contributed by Kirti
     

输出

5th centered decagonalnumber: 151
9th centered decagonalnumber: 451