Icosidigonal number
Last Updated :
20 May, 2022
Given a number n, the task is to find the nth Icosidigonal number (Isdn).
The polygon has the many gons, depends on their gonal number series. In mathematics, there is a number of gonal numbers and the icosidigonal number is one of them and these numbers have 22 -sided polygon (icosidigon). An icosidigonal number belong to the class of figurative number. They have one common dots points and other dots pattern is arranged in an n-th nested icosidigon pattern.
Examples :
Input : 2
Output :22
Input :6
Output :306
Formula for nth Icosidigonal number:
C++
#include <bits/stdc++.h>
using namespace std;
int icosidigonal_num( long int n)
{
return (20 * n * n - 18 * n) / 2;
}
int main()
{
long int n = 4;
cout << n << "th Icosidigonal number :" << icosidigonal_num(n);
cout << endl;
n = 8;
cout << n << "th Icosidigonal number:" << icosidigonal_num(n);
return 0;
}
|
C
#include <stdio.h>
int icosidigonal_num( long int n)
{
return (20 * n * n - 18 * n) / 2;
}
int main()
{
long int n = 4;
printf ( "%ldth Icosidigonal number : %d\n" ,n,icosidigonal_num(n));
n = 8;
printf ( "%ldth Icosidigonal number : %d\n" ,n,icosidigonal_num(n));
return 0;
}
|
Java
import java.io.*;
class GFG
{
static int icosidigonal_num( int n)
{
return ( 20 * n * n - 18 * n) / 2 ;
}
public static void main (String[] args)
{
int n = 4 ;
System.out.print (n + "th Icosidigonal number :" );
System.out.println (icosidigonal_num(n));
n = 8 ;
System.out.print (n + "th Icosidigonal number :" );
System.out.println (icosidigonal_num(n));
}
}
|
Python 3
def icosidigonal_num(n) :
return ( 20 * n * n -
18 * n) / / 2
if __name__ = = '__main__' :
n = 4
print (n, "th Icosidigonal " +
"number : " ,
icosidigonal_num(n))
n = 8
print (n, "th Icosidigonal " +
"number : " ,
icosidigonal_num(n))
|
C#
using System;
class GFG
{
static int icosidigonal_num( int n)
{
return (20 * n * n -
18 * n) / 2;
}
static public void Main ()
{
int n = 4;
Console.Write(n + "th Icosidigonal " +
"number :" );
Console.WriteLine(icosidigonal_num(n));
n = 8;
Console.Write (n + "th Icosidigonal " +
"number :" );
Console.WriteLine(icosidigonal_num(n));
}
}
|
PHP
<?php
function icosidigonal_num( $n )
{
return (20 * $n * $n - 18 * $n ) / 2;
}
$n = 4;
echo $n , "th Icosidigonal number : " ,
icosidigonal_num( $n );
echo "\n" ;
$n = 8;
echo $n , "th Icosidigonal number : " ,
icosidigonal_num( $n );
?>
|
Javascript
<script>
function icosidigonal_num(n)
{
return parseInt((20 * n * n - 18 * n) / 2);
}
let n = 4;
document.write(n + "th Icosidigonal number :" + icosidigonal_num(n));
document.write( "<br>" );
n = 8;
document.write(n + "th Icosidigonal number :" + icosidigonal_num(n));
</script>
|
Output :
4th Icosidigonal number :124
8th Icosidigonal number:568
Time Complexity: O(1)
Auxiliary Space: O(1)
Reference: https://en.wikipedia.org/wiki/Polygonal_number
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