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

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` `?>` |

## Javascript

`<script>` `// Javascript Program to find n-th rectangular number` `// Returns n-th rectangular number` `function` `findRectNum(n)` `{` ` ` `return` `n * (n + 1);` `}` `// Driver code` `var` `n = 6;` `document.write(findRectNum(n));` `// This code is contributed by noob2000.` `</script>` |

Output:

42

Check if a given number is Pronic | Efficient Approach

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