You are given a number n, the task is to find the nth Decagonal number. A decagonal number is a figurate number that extends the concept of triangular and square numbers to the decagon (a ten-sided polygon). The nth decagonal numbers counts the number of dots in a pattern of n nested decagons, all sharing a common corner, where the ith decagon in the pattern has sides made of i dots spaced one unit apart from each other.
Input : n = 3
Output : 27
Input : n = 7
Output : 175
The n-th decagonal number is given by the formula
(4n 2 – 3n).
C++
#include <bits/stdc++.h>
using namespace std;
int decagonal( int n)
{
return 4 * n * n - 3 * n;
}
int main()
{
int n = 10;
cout << n << "th decagonal number :" << decagonal(n);
return 0;
}
|
Java
import java.util.*;
class GFG {
static int decagonal( int n)
{
return 4 * n * n - 3 * n;
}
public static void main(String[] args)
{
int n = 10 ;
System.out.println(n + "th decagonal number :"
+ decagonal(n));
}
}
|
Python
def decagonal(n):
return 4 * n * n - 3 * n
n = 10
print (n, "th decagonal number :" , decagonal(n))
|
C#
using System;
class GFG {
static int decagonal( int n)
{
return 4 * n * n - 3 * n;
}
public static void Main()
{
int n = 10;
Console.Write(n + "th decagonal number : "
+ decagonal(n));
}
}
|
PHP
<?php
function decagonal( $n )
{
return 4 * $n * $n - 3 * $n ;
}
$n = 10;
echo $n , "th decagonal number :" ,
decagonal( $n );
?>
|
Javascript
<script>
function decagonal(n)
{
return 4 * n * n - 3 * n;
}
let n = 10;
document.write(n + "th decagonal number : " +
decagonal(n));
</script>
|
10th decagonal number : 370
Time Complexity: O(1)
Auxiliary Space: O(1)