Octadecagonal Number
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++
// 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
// 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
# 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#
// 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 |
Javascript
<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