257-gon number

给定数字N ，任务是找到^第N^个257-gon数。

A 257-gon number is a class of figurate numbers. It has a 257-sided polygon called 257-gon. The N-th 257-gon number count’s the 257 number of dots and all other dots are surrounding with a common sharing corner and make a pattern. The first few 257-gon numbers are 1, 257, 768, 1534, 2555, 3831, … 
 

例子：

Input: N = 2 
Output: 257 
Explanation: 
The second 257-gonol number is 257. 
Input: N = 3 
Output: 768 
 

方法：第N 257-gon数由以下公式给出：

• 侧多边形的第N个项= $\frac{((s-2)n^2 - (s-4)n)}{2}$
• 因此257个多边形的第N个项是

$Tn =\frac{((257-2)n^2 - (257-4)n)}{2} =\frac{(255^2 - 253)}{2}$

下面是上述方法的实现：

C++

// C++ implementation for
// above approach
#include 
using namespace std;
 
// Function to find the
// nth 257-gon Number
int gonNum257(int n)
{
    return (255 * n * n - 253 * n) / 2;
}
 
// Driver Code
int main()
{
    int n = 3;
    cout << gonNum257(n);
 
    return 0;
}

Java

// Java program for above approach
class GFG{
 
// Function to find the
// nth 257-gon Number
static int gonNum257(int n)
{
    return (255 * n * n - 253 * n) / 2;
}
 
// Driver code
public static void main(String[] args)
{
    int n = 3;
    System.out.print(gonNum257(n));
}
}
 
// This code is contributed by shubham

Python3

# Python3 implementation for
# above approach
 
# Function to find the
# nth 257-gon Number
def gonNum257(n):
 
    return (255 * n * n - 253 * n) // 2;
 
# Driver Code
n = 3;
print(gonNum257(n));
 
# This code is contributed by Code_Mech

C#

// C# program for above approach
using System;
class GFG{
 
// Function to find the
// nth 257-gon Number
static int gonNum257(int n)
{
    return (255 * n * n - 253 * n) / 2;
}
 
// Driver code
public static void Main(String[] args)
{
    int n = 3;
    Console.Write(gonNum257(n));
}
}
 
// This code is contributed by sapnasingh4991

Javascript

 
 
// JavaScript implementation for
// above approach
 
// Function to find the
// nth 257-gon Number
function gonNum257(n)
{
    return (255 * n * n - 253 * n) / 2;
}
 
// Driver Code
var n = 3;
document.write(gonNum257(n));
 
 

输出：

768

参考： https ： //en.wikipedia.org/wiki/257-gon