Icositrigonal Number

Given a number N, the task is to find Nth Icositrigonal number or not.

An Icositrigonal number is class of figurate number. It has 23 – sided polygon called Icositrigon. The N-th Icositrigonal number count’s the 23 number of dots and all others dots are surrounding with a common sharing corner and make a pattern. The first few Icositrigonol numbers are 1, 23, 66, 130, 215, 321, 448 …

Examples:

Input: N = 2
Output: 23
Explanation:
The second Icositrigonol number is 66.

Input: N = 6
Output: 321



Approach: The N-th Icositrigonal number is given by the formula:

Tn = (21n^2 - 19n)/2

Below is the implementation of the above approach:

C++

filter_none

edit
close

play_arrow

link
brightness_4
code

// C++ program to find nth 
// Icositrigonal number 
  
#include <bits/stdc++.h> 
using namespace std; 
  
// Function to find N-th 
// Icositrigonal number 
int Icositrigonal_num(int n) 
    // Formula to calculate nth 
    // Icositrigonal number 
    return (21 * n * n - 19 * n) / 2; 
  
// Driver Code 
int main() 
    int n = 3; 
    cout << Icositrigonal_num(n) << endl; 
      
    n = 10; 
    cout << Icositrigonal_num(n); 
  
    return 0; 

chevron_right


Java

filter_none

edit
close

play_arrow

link
brightness_4
code

// Java program to find nth 
// Icositrigonal number 
class GFG{
  
// Function to find N-th 
// Icositrigonal number    
static int IcositrigonalNum(int n)
      
    // Formula to calculate nth 
    // Icositrigonal number 
    return (21 * n * n - 19 * n) / 2
}
  
// Driver code
public static void main(String[] args)
{
    int n = 3;
    System.out.print(IcositrigonalNum(n) + "\n");
      
    n = 10;
    System.out.print(IcositrigonalNum(n));
}
}
  
// This code is contributed by spp____

chevron_right


Python3

filter_none

edit
close

play_arrow

link
brightness_4
code

# Python3 program to find nth 
# Icositrigonal number 
  
# Function to find N-th 
# Icositrigonal number 
def IcositrigonalNum(n):
      
    # Formula to calculate nth 
    # Icositrigonal number 
    return (21 * n * n - 19 * n) / 2
  
# Driver code
n = 3
print(IcositrigonalNum(n))
  
n = 10
print(IcositrigonalNum(n))
  
# This code is contributed by spp____

chevron_right


C#

filter_none

edit
close

play_arrow

link
brightness_4
code

// C# program to find nth 
// Icositrigonal number 
using System;
  
class GFG{
  
// Function to find N-th 
// Icositrigonal number     
static int IcositrigonalNum(int n)
{
      
    // Formula to calculate nth 
    // Icositrigonal number 
    return (21 * n * n - 19 * n) / 2; 
}
  
// Driver code
public static void Main()
{
    int n = 3;
    Console.WriteLine(IcositrigonalNum(n));
      
    n = 10;
    Console.WriteLine(IcositrigonalNum(n));
}
}
  
// This code is contributed by spp____

chevron_right


Output:

66
955

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

Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.




My Personal Notes arrow_drop_up

Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.



Improved By : spp____

Article Tags :
Practice Tags :


Be the First to upvote.


Please write to us at contribute@geeksforgeeks.org to report any issue with the above content.