# Icositrigonal Number

Last Updated : 17 Mar, 2021

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 countâ€™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:

Below is the implementation of the above approach:

## C++

 // C++ program to find nth // Icositrigonal number  #include 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; }

## Java

 // 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 codepublic 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____

## Python3

 # 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 coden = 3print(IcositrigonalNum(n)) n = 10print(IcositrigonalNum(n)) # This code is contributed by spp____

## C#

 // 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 codepublic static void Main(){    int n = 3;    Console.WriteLine(IcositrigonalNum(n));         n = 10;    Console.WriteLine(IcositrigonalNum(n));}} // This code is contributed by spp____

## Javascript

 

Output:
66
955

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