中心三边形数

给定数字n，任务是找到第n个居中的三边形数。
居中的三边形数字代表中心的一个点，以及围绕该中心点的其他点
在连续的十三边形(13面多边形)层中。

例子 ：

Input : 2 
Output : 14

Input : 9 
Output : 469 
 

第n个居中三边形数字的公式：

$CT_{n}= (13n(n-1)+2)/2$

C++

// C++ Program to find nth
// centered tridecagonal number
#include 
using namespace std;
 
// Function to find nth centered
// tridecagonal number
int centeredTridecagonalNum(long int n)
{
    // Formula to calculate nth
    // centered tridecagonal number
    return (13 * n * (n - 1) + 2) / 2;
}
 
// Drivers code
int main()
{
    long int n = 3;
    cout << centeredTridecagonalNum(n);
    cout << endl;
    n = 10;
    cout << centeredTridecagonalNum(n);
 
    return 0;
}

Java

// Java Program to find nth
// centered tridecagonal number
import java.io.*;
 
class GFG
{
 
// Function to find nth centered
// tridecagonal number
static long centeredTridecagonalNum(long n)
{
    // Formula to calculate nth
    // centered tridecagonal number
    return (13 * n * (n - 1) + 2) / 2;
}
 
// Driver Code
public static void main (String[] args)
{
    long n = 3;
    System.out.println(centeredTridecagonalNum(n));
    n = 10;
    System.out.println(centeredTridecagonalNum(n));
}
}
 
// This code is contributed by anuj_67.

Python3

# Program to find nth centered
# tridecagonal number
 
# Function to find centered
# tridecagonal number
def centeredTridecagonalNum(n) :
     
    # Formula to calculate nth
    # centered tridecagonal number
    return (13 * n *
           (n - 1) + 2) // 2
 
# Driver Code
if __name__ == '__main__' :
         
    n = 3
    print(centeredTridecagonalNum(n))
    n = 10
    print(centeredTridecagonalNum(n))
                 
# This code is contributed
# by akt_mit

C#

// C# Program to find nth
// centered tridecagonal number
using System;
 
class GFG
{
 
// Function to find nth centered
// tridecagonal number
static long centeredTridecagonalNum(long n)
{
    // Formula to calculate nth
    // centered tridecagonal number
    return (13 * n * (n - 1) + 2) / 2;
}
 
// Driver Code
public static void Main ()
{
    long n = 3;
    Console.WriteLine(centeredTridecagonalNum(n));
    n = 10;
    Console.WriteLine(centeredTridecagonalNum(n));
}
}
 
// This code is contributed by anuj_67.

Javascript

 
// Javascript program to find nth
// centered tridecagonal number
 
// Function to find nth centered
// tridecagonal number
function centeredTridecagonalNum(n)
{
     
    // Formula to calculate nth
    // centered tridecagonal number
    return (13 * n * (n - 1) + 2) / 2;
}
 
// Driver code
var n = 3;
document.write(centeredTridecagonalNum(n) + "<br>");
  
n = 10;
document.write(centeredTridecagonalNum(n));
 
// This code is contributed by Ankita saini
 

输出 ：

40
586

参考：http：//oeis.org/wiki/Figurate_numbers