Given a number n, find the nth centered octagonal number.
A centered octagonal number represents an octagon with a dot in the center and others dots surrounding the center dot in the successive octagonal layer.
Examples :
Input : 2 Output : 9 Input : 5 Output : 81
Centered Octagonal n-th Number is given by :
Basic Implementation of the above approach:
C++
// Program to find nth // centered octagonal // number #include <bits/stdc++.h> using namespace std;
// Centered octagonal number function int cen_octagonalnum( long int n)
{ // Formula to calculate nth
// centered octagonal number &
// return it into main function.
return (4 * n * n - 4 * n + 1);
} // Driver Code int main()
{ long int n = 6;
cout << n << "th centered"
<< " octagonal number : " ;
cout << cen_octagonalnum(n);
cout << endl;
n = 11;
cout << n << "th centered"
<< " octagonal number : " ;
cout << cen_octagonalnum(n);
return 0;
} |
C
// C Program to find nth // centered octagonal // number #include <stdio.h> // Centered octagonal number function int cen_octagonalnum( long int n)
{ // Formula to calculate nth
// centered octagonal number &
// return it into main function.
return (4 * n * n - 4 * n + 1);
} // Driver Code int main()
{ long int n = 6;
printf ( "%ldth centered octagonal number : " ,n);
printf ( "%d\n" ,cen_octagonalnum(n));
n = 11;
printf ( "%ldth centered octagonal number : " ,n);
printf ( "%d\n" ,cen_octagonalnum(n));
return 0;
} // This code is contributed by kothavvsaakash. |
Java
// Java Program to find nth // centered octagonal number import java.io.*;
class GFG
{ // Function to find centered
// octagonal number
static int centeredoctagonalNumber( int n)
{
// Formula to calculate nth
// centered octagonal number
// and return it into main function
return 4 * n * (n - 1 ) + 1 ;
}
// Driver Code
public static void main(String args[])
{
int n = 6 ;
System.out.print(n + "th centered " +
"octagonal number: " );
System.out.println(
centeredoctagonalNumber(n));
n = 11 ;
System.out.print(n + "th centered " +
"octagonal number: " );
System.out.println(
centeredoctagonalNumber(n));
}
} // This code has been contributed by Prasad_Kshirsagar. |
Python3
# Program to find nth # centered octagonal number def cen_octagonalnum(n) :
# Formula to calculate nth
# centered octagonal number
return ( 4 * n * n -
4 * n + 1 )
# Driver Code if __name__ = = '__main__' :
n = 6
print (n, "th Centered" ,
"octagonal number: " ,
cen_octagonalnum(n))
n = 11
print (n, "th Centered" ,
"octagonal number: " ,
cen_octagonalnum(n))
# This code is contributed # by akt_mit |
C#
// Program to find nth centered octagonal // number using System;
public class GFG{
// Centered octagonal number function
static long cen_octagonalnum( long n)
{
// Formula to calculate nth
// centered octagonal number &
// return it into main function.
return (4 * n * n - 4 * n + 1);
}
// Driver code
static public void Main ()
{
long n = 6;
Console.WriteLine(n + "th centered"
+ " octagonal number : "
+ cen_octagonalnum(n));
n = 11;
Console.WriteLine(n + "th centered"
+ " octagonal number : "
+ cen_octagonalnum(n));
}
} // This code is contributed by anuj_67. |
PHP
<?php // Program to find nth // centered octagonal // number // Centered octagonal // number function function cen_octagonalnum( $n )
{ // Formula to calculate nth
// centered octagonal number &
// return it into main function.
return (4 * $n * $n -
4 * $n + 1);
} // Driver Code $n = 6;
echo $n , "th centered" ,
" octagonal number : " ;
echo cen_octagonalnum( $n );
echo "\n" ;
$n = 11;
echo $n , "th centered" ,
" octagonal number : " ;
echo cen_octagonalnum( $n );
// This code is contributed by ajit ?> |
Javascript
<script> // Javascript Program to find nth // centered octagonal number // Function to find centered // octagonal number function centeredoctagonalNumber(n)
{ // Formula to calculate nth
// centered octagonal number
// and return it into main function
return 4 * n * (n - 1) + 1;
} // Driver Code var n = 6;
document.write(n + "th centered " +
"octagonal number: " );
document.write(centeredoctagonalNumber(n) + "<br>" );
n = 11; document.write(n + "th centered " +
"octagonal number: " );
document.write(centeredoctagonalNumber(n)); // This code is contributed by Kirti </script> |
Output
6th centered octagonal number : 121 11th centered octagonal number : 441
Time Complexity: O(1)
Auxiliary Space: O(1)