Triacontagon Number

Given a number N, the task is to find N^th Triacontagon number.

An Triacontagon number is class of figurate number. It has 30 – sided polygon called triacontagon. The N-th triacontagonal number count’s the 30 number of dots and all others dots are surrounding with a common sharing corner and make a pattern. The first few triacontagonol numbers are 1, 30, 87, 172 …

Examples:

Input: N = 2 
Output: 30 
Explanation:
The second triacontagonol number is 30. 
Input: N = 3 
Output: 87 

Approach: The N-th triacontagonal number is given by the formula:

• Nth term of s sided polygon = 
  
• Therefore Nth term of 30 sided polygon is
  

• 
  

Below is the implementation of the above approach: 

C++

// C++ program for above approach
#include <bits/stdc++.h>
using namespace std;

// Finding the nth triacontagonal number
int triacontagonalNum(int n)
{
    return (28 * n * n - 26 * n) / 2;
}

// Driver code
int main()
{
    int n = 3;

    cout << "3rd triacontagonal Number is = "
         << triacontagonalNum(n);

    return 0;
}

// This code is contributed by shivanisinghss2110

C

// C program for above approach
#include <stdio.h>
#include <stdlib.h>

// Finding the nth triacontagonal Number
int triacontagonalNum(int n)
{
    return (28 * n * n - 26 * n) / 2;
}

// Driver program to test above function
int main()
{
    int n = 3;
    printf("3rd triacontagonal Number is = %d",
           triacontagonalNum(n));

    return 0;
}

Java

// Java program for above approach
import java.io.*;
import java.util.*;

class GFG {

// Finding the nth triacontagonal number
static int triacontagonalNum(int n)
{
    return (28 * n * n - 26 * n) / 2;
}

// Driver code
public static void main(String[] args)
{
    int n = 3;

    System.out.println("3rd triacontagonal Number is = " +
                                    triacontagonalNum(n));
}
}

// This code is contributed by coder001

Python3

# Python3 program for above approach

# Finding the nth triacontagonal Number
def triacontagonalNum(n):

    return (28 * n * n - 26 * n) // 2

# Driver Code
n = 3
print("3rd triacontagonal Number is = ",
                   triacontagonalNum(n))

# This code is contributed by divyamohan123

C#

// C# program for above approach
using System;

class GFG{

// Finding the nth triacontagonal number
static int triacontagonalNum(int n)
{
    return (28 * n * n - 26 * n) / 2;
}

// Driver code
public static void Main()
{
    int n = 3;

    Console.Write("3rd triacontagonal Number is = " +
                               triacontagonalNum(n));
}
}

// This code is contributed by Akanksha_Rai

Javascript

<script>


// JavaScript program for above approach

// Finding the nth triacontagonal number
function triacontagonalNum(n)
{
    return (28 * n * n - 26 * n) / 2;
}

// Driver code
var n = 3;
document.write("3rd triacontagonal Number is = " + triacontagonalNum(n));


</script>

Output:

3rd triacontagonal Number is = 87

Time Complexity: O(1)

Auxiliary Space: O(1)

Reference: https://en.wikipedia.org/wiki/Triacontagon