Icosikaipentagon数

给定数字N ，任务是找到^第N^个icosikaipentagon数。

An icosikaipentagon number is class of figurate number. It has 25- sided polygon called icosikaipentagon. The N-th icosikaipentagon number count’s the 25 number of dots and all others dots are surrounding with a common sharing corner and make a pattern. The first few icosikaipentagonol numbers are 1, 25, 72, 142 … 
 

例子：

Input: N = 2 
Output: 25 
Explanation: 
The second icosikaipentagonol number is 25. 

Input: N = 3 
Output: 72 

方法：第N个二十烷五角形数由下式给出：

• S面多边形的第N个项= $\frac{((S - 2)N^2 - (S - 4)N)}{2}$
• 因此，25个面的多边形的第N个项由下式给出：

$Tn =\frac{((25 - 2)N^2 - (25 - 4)N)}{2} =\frac{(23N^2 - 21N)}{2}$

下面是上述方法的实现：

C++

// C++ program to find the N-th
// Icosikaipentagon Number
   
#include 
using namespace std;
   
// Function to find the N-th
// icosikaipentagon Number
int icosikaipentagonNum(int N)
{
    return (23 * N * N - 21 * N)
           / 2;
}
   
// Driver code
int main()
{
    int n = 3;
    cout << "3rd icosikaipentagon Number is "
         << icosikaipentagonNum(n);
   
    return 0;
}

Java

// Java program to find N-th
// icosikaipentagon number
class GFG{
 
// Function to find the nth
// icosikaipentagon number
static int icosikaipentagonNum(int N)
{
    return (23 * N * N - 21 * N) / 2;
}
 
// Driver code
public static void main(String[] args)
{
    int n = 3;
    System.out.print("3rd icosikaipentagon Number is " +
                                icosikaipentagonNum(n));
}
}
 
// This code is contributed by shubham

Python3

# Python3 program to find the N-th
# icosikaipentagon number
 
# Function to find the N-th
# icosikaipentagon number
def icosikaipentagonNum(N):
 
    return (23 * N * N - 21 * N) // 2
 
# Driver code
n = 3
print("3rd icosikaipentagon Number is ",
                 icosikaipentagonNum(n))
 
# This code is contributed by yatinagg

C#

// C# program for the above approach
using System;
class GFG{
 
// Finding the nth chiliagon number
static int Icosikaipentagon(int n)
{
    return (23 * n * n - 21 * n) / 2;
}
 
// Driver code
public static void Main()
{
    int n = 3;
    Console.Write("3rd Icosikaipentagon Number is = " +
                                  Icosikaipentagon(n));
}
}
 
// This code is contributed by shivanisinghss2110

Javascript

// Javascript program to find the N-th
// Icosikaipentagon Number
   
// Function to find the N-th
// icosikaipentagon Number
function icosikaipentagonNum(N)
{
    return parseInt((23 * N * N - 21 * N)
           / 2);
}
   
// Driver code
let n = 3;
document.write("3rd icosikaipentagon Number is "
    + icosikaipentagonNum(n));
     
    // This code is contributed by rishavmahato348.

输出：

3rd icosikaipentagon Number is 72

时间复杂度： O(1)

辅助空间： O(1)

参考： http : //www.2dcurves.com/line/linep.html