Icosagonal number

Given a number n, the task is to find the nth Icosagonal number.
An Icosagonal number is the 20-gon is a twenty-sided polygon. The number derived from the figurative class. There are different pattern series number in this number. The dots are countable, arrange in a specific way of position and create a diagram. All the dots have a common dots points, all others dots are connected to this points and except this common point the dots connected to their i-th dots with their respective successive layer.

Examples :

Input : 3
Output :57



Input :8
Output :512

icosagonal number

Formula for nth icosagonal number:

  \begin{math}  Ig_{n}=((18n^2)-16n)/2 \end{math}  

C++

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// C++ program to find
// nth Icosagonal number
#include <bits/stdc++.h>
using namespace std;
  
// Function to calculate Icosagonal number
int icosagonal_poly(long int n)
{
    // Formula for finding
    // nth Icosagonal number
    return (18 * n * n - 16 * n) / 2;
}
  
// Drivers code
int main()
{
    long int n = 7;
    cout << n << "th Icosagonal number :" 
               << icosagonal_poly(n);
  
    return 0;
}

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Java

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// Java program to find
// nth Icosagonal number
  
import java.io.*;
  
class GFG {
      
// Function to calculate Icosagonal number
  
static int icosagonal_poly(int n)
{
    // Formula for finding
    // nth Icosagonal number
    return (18 * n * n - 16 * n) / 2;
}
  
// Drivers code
      
    public static void main (String[] args) {
     
    int n = 7;
      
    System.out.print (n + "th Icosagonal number :");
    System.out.println(icosagonal_poly(n));
    }
}
// This code is contributed by aj_36

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Python 3

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# Python 3 program to find 
# nth Icosagonal number
  
# Function to calculate
# Icosagonal number
def icosagonal_poly(n) :
      
    # Formula for finding
    # nth Icosagonal number
    return (18 * n * n - 
            16 * n) // 2
  
# Driver Code
if __name__ == '__main__' :
    n = 7
    print(n,"th Icosagonal number : "
                   icosagonal_poly(n))
  
# This code is contributed m_kit

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C#

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// C# program to find
// nth Icosagonal number
using System;
  
class GFG
{
  
// Function to calculate
// Icosagonal number
static int icosagonal_poly(int n)
{
    // Formula for finding
    // nth Icosagonal number
    return (18 * n * n - 
            16 * n) / 2;
}
  
// Driver code
static public void Main ()
{
      
int n = 7;
  
Console.Write(n + "th Icosagonal " +
                        "number :");
Console.WriteLine(icosagonal_poly(n));
}
}
  
// This code is contributed by ajit

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PHP

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<?php
// PHP program to find
// nth Icosagonal number
  
// Function to calculate
// Icosagonal number
function icosagonal_poly($n)
{
    // Formula for finding
    // nth Icosagonal number
    return (18 * $n
            $n - 16 * $n) / 2;
}
  
// Driver Code
$n = 7;
echo $n , "th Icosagonal number :",
               icosagonal_poly($n);
  
// This code is contributed by ajit
?>

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Output :

7th Icosagonal number :385

Reference: https://en.wikipedia.org/wiki/Polygonal_number



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Improved By : jit_t