Rectangular (or Pronic) Numbers

The numbers that can be arranged to form a rectangle are called Rectangular Numbers (also known as Pronic numbers). The first few rectangular numbers are:
0, 2, 6, 12, 20, 30, 42, 56, 72, 90, 110, 132, 156, 182, 210, 240, 272, 306, 342, 380, 420, 462 . . . . . .

Given a number n, find n-th rectangular number.

Examples:

Input : 1
Output : 2

Input : 4
Output : 20

Input : 5
Output : 30

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

The number 2 is a rectangular number because it is 1 row by 2 columns. The number 6 is a rectangular number because it is 2 rows by 3 columns, and the number 12 is a rectangular number because it is 3 rows by 4 columns.

If we observe these numbers carefully, we can notice that n-th rectangular number is n(n+1).

C++

// CPP Program to find n-th rectangular number 
#include <bits/stdc++.h> 
using namespace std; 
  
// Returns n-th rectangular number 
int findRectNum(int n) 
{ 
    return n * (n + 1); 
} 
  
// Driver code 
int main() 
{ 
    int n = 6; 
    cout << findRectNum(n); 
    return 0; 
} 

Java

// Java Program to find n-th rectangular number 
import java.io.*; 
  
class GFG { 
  
    // Returns n-th rectangular number 
    static int findRectNum(int n) 
    { 
        return n * (n + 1); 
    } 
  
    // Driver code 
    public static void main(String[] args) 
    { 
        int n = 6; 
        System.out.println(findRectNum(n)); 
    } 
} 
  
// This code is contributed by vt_m. 

C#

// C# Program to find n-th rectangular number 
  
using System; 
  
class GFG { 
  
    // Returns n-th rectangular number 
    static int findRectNum(int n) 
    { 
        return n * (n + 1); 
    } 
  
    // Driver code 
    public static void Main() 
    { 
        int n = 6; 
        Console.Write(findRectNum(n)); 
    } 
} 
  
// This code is contributed by vt_m. 

Python

# Python3 Program to find n-th rectangular number 
  
# Returns n-th rectangular number 
def findRectNum(n): 
    return n*(n + 1) 
  
# Driver code  
n = 6
print (findRectNum(n)) 
  
# This code is contributed by Shreyanshi Arun. 

PHP

<?php 
// PHP Program to find n-th 
// rectangular number 
  
// Returns n-th rectangular 
// number 
function findRectNum($n) 
{ 
    return $n * ($n + 1); 
} 
  
    // Driver Code 
    $n = 6; 
    echo findRectNum($n); 
      
// This code is contributed by ajit 
?> 

Output:

Check if a given number is Pronic | Efficient Approach

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My Personal Notes

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

C++

Java

C#

Python

PHP

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