Hendecagonal number
Last Updated :
19 May, 2022
Given a number n, the task is to find the nth Hendecagonal number.
A Hendecagonal number is a figurate number that extends the concept of triangular and square numbers to the decagon (Eleven -sided polygon). The nth hendecagonal number counts the number of dots in a pattern of n nested decagons, all sharing a common corner, where the ith hendecagon in the pattern has sides made of i dots spaced one unit apart from each other.
Examples:
Input : 2
Output :11
Input :6
Output :141
Formula for nth hendecagonal number :
C++
#include <bits/stdc++.h>
using namespace std;
int hendecagonal_num( int n)
{
return (9 * n * n - 7 * n) / 2;
}
int main()
{
int n = 3;
cout << n << "rd Hendecagonal number: " ;
cout << hendecagonal_num(n);
cout << endl;
n = 10;
cout << n << "th Hendecagonal number: " ;
cout << hendecagonal_num(n);
return 0;
}
|
C
#include <stdio.h>
int hendecagonal_num( int n)
{
return (9 * n * n - 7 * n) / 2;
}
int main()
{
int n = 3;
printf ( "%drd Hendecagonal number: " ,n);
printf ( "%d\n" ,hendecagonal_num(n));
n = 10;
printf ( "%dth Hendecagonal number: " ,n);
printf ( "%d\n" ,hendecagonal_num(n));
return 0;
}
|
Java
import java.io.*;
class GFG
{
static int hendecagonal_num( int n)
{
return ( 9 * n * n -
7 * n) / 2 ;
}
public static void main (String[] args)
{
int n = 3 ;
System.out.print(n + "rd Hendecagonal " +
"number: " );
System.out.println(hendecagonal_num(n));
n = 10 ;
System.out.print(n + "th Hendecagonal " +
"number: " );
System.out.println(hendecagonal_num(n));
}
}
|
Python3
def hendecagonal_num(n) :
return ( 9 * n * n -
7 * n) / / 2
if __name__ = = '__main__' :
n = 3
print (n, "rd Hendecagonal number : " ,
hendecagonal_num(n))
n = 10
print (n, "th Hendecagonal number : " ,
hendecagonal_num(n))
|
C#
using System;
class GFG
{
static int hendecagonal_num( int n)
{
return (9 * n * n - 7 * n) / 2;
}
static public void Main ()
{
int n = 3;
Console.Write(n +
"rd Hendecagonal number: " );
Console.WriteLine( hendecagonal_num(n));
n = 10;
Console.Write(n +
"th Hendecagonal number: " );
Console.WriteLine( hendecagonal_num(n));
}
}
|
PHP
<?php
function hendecagonal_num( $n )
{
return (9 * $n * $n - 7 * $n ) / 2;
}
$n = 3;
echo $n , "th Hendecagonal number: " ;
echo hendecagonal_num( $n );
echo "\n" ;
$n = 10;
echo $n , "th Hendecagonal number: " ;
echo hendecagonal_num( $n );
?>
|
Javascript
<script>
function hendecagonal_num(n)
{
return (9 * n * n - 7 * n) / 2;
}
let n = 3;
document.write(n + "rd Hendecagonal number: " );
document.write(hendecagonal_num(n) + "</br>" );
n = 10;
document.write(n + "th Hendecagonal number: " );
document.write(hendecagonal_num(n));
</script>
|
Output :
3th Hendecagonal number: 30
10th Hendecagonal number: 415
Time Complexity: O(1)
Auxiliary Space: O(1)
Reference: https://en.wikipedia.org/wiki/Polygonal_number
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