Given a number N, the task is to find the Nth Octadecagonal number.
An Octadecagonal number is a class of figurate numbers. It has 18 – sided polygon called Octadecagon. The Nth Octadecagonal number count’s the eighteen number of dots and all other dots are surrounding with a common sharing corner and make a pattern. The first few Octadecagonal numbers are 1, 18, 51, 100, 165, 246, 343 …
Examples:
Input: N = 2
Output: 18
Explanation:
The second octadecagonal number is 18.
Input: N = 6
Output: 246
Approach: The Nth Octadecagonal number is given by the formula:
Below is the implementation of the above approach:
// C++ program to find Nth // Octadecagonal number #include <bits/stdc++.h> using namespace std;
// Function to find N-th // Octadecagonal number int Octadecagonal_num( int n)
{ // Formula to calculate nth
// Octadecagonal number
return (16 * n * n - 14 * n) / 2;
} // Driver code int main()
{ int n = 3;
cout << Octadecagonal_num(n) << endl;
n = 10;
cout << Octadecagonal_num(n) << endl;
return 0;
} |
// Java program to find Nth // octadecagonal number import java.io.*;
import java.util.*;
class GFG{
// Function to find N-th // octadecagonal number static int Octadecagonal_num( int n)
{ // Formula to calculate nth
// octadecagonal number
return ( 16 * n * n - 14 * n) / 2 ;
} // Driver code public static void main(String[] args)
{ int n = 3 ;
System.out.println(Octadecagonal_num(n));
n = 10 ;
System.out.println(Octadecagonal_num(n));
} } // This code is contributed by coder001 |
# Python3 program to find Nth # octadecagonal number # Function to find N-th # octadecagonal number def Octadecagonal_num(n):
# Formula to calculate nth
# octadecagonal number
return ( 16 * n * n - 14 * n) / 2
# Driver code n = 3
print ( int (Octadecagonal_num(n)))
n = 10
print ( int (Octadecagonal_num(n)))
# This code is contributed by divyeshrabadiya07 |
// C# program to find Nth // octadecagonal number using System;
class GFG{
// Function to find N-th // octadecagonal number static int Octadecagonal_num( int n)
{ // Formula to calculate nth
// octadecagonal number
return (16 * n * n - 14 * n) / 2;
} // Driver code public static void Main( string [] args)
{ int n = 3;
Console.Write(Octadecagonal_num(n) + "\n" );
n = 10;
Console.Write(Octadecagonal_num(n) + "\n" );
} } // This code is contributed by rutvik_56 |
<script> // Javascript program to find Nth
// Octadecagonal number
// Function to find N-th
// Octadecagonal number
function Octadecagonal_num(n)
{
// Formula to calculate nth
// Octadecagonal number
return (16 * n * n - 14 * n) / 2;
}
let n = 3;
document.write(Octadecagonal_num(n) + "</br>" );
n = 10;
document.write(Octadecagonal_num(n));
// This code is contributed by divyesh072019.
</script> |
Output:
51 730
Reference: https://en.wikipedia.org/wiki/Polygonal_number