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.
Examples:
Input : n = 3 Output : 27 Input : n = 7 Output : 175
The n-th decagonal number is given by the formula
(4n 2 – 3n).
C++
// C++ program to find nth decagonal number#include <bits/stdc++.h>using namespace std; // Function to calculate decagonal numberint decagonal(int n){ // Formula for finding nth decagonal number return 4 * n * n - 3 * n;} // Driver functionint main(){ int n = 10; cout << n << "th decagonal number :" << decagonal(n); return 0;} |
Java
// JAVA Code for Decagonal Numbersimport java.util.*;class GFG { // Function to calculate // decagonal number static int decagonal(int n) { // Formula for finding nth // decagonal number return 4 * n * n - 3 * n; } /* Driver function */ public static void main(String[] args) { int n = 10; System.out.println(n + "th decagonal number :" + decagonal(n)); }}// This code is contributed by Arnav Kr. Mandal. |
Python
# Python program to find nth decagonal numberdef decagonal(n): return 4 * n * n - 3 * n # Driver coden = 10print(n, "th decagonal number :", decagonal(n)) |
C#
// C# Code for Decagonal Numbersusing System;class GFG { // Function to calculate // decagonal number static int decagonal(int n) { // Formula for finding nth // decagonal number return 4 * n * n - 3 * n; } // Driver Code public static void Main() { int n = 10; Console.Write(n + "th decagonal number : " + decagonal(n)); }}// This code is contributed by vt_m. |
PHP
<?php// PHP program to find nth// decagonal number// Function to calculate// decagonal numberfunction decagonal($n){ // Formula for finding nth // decagonal number return 4 * $n * $n - 3 * $n;}// Driver function$n = 10;echo $n, "th decagonal number :", decagonal($n);// This code is contributed by ajit?> |
Javascript
<script>// JavaScript program for Decagonal Numbers// Function to calculate // decagonal numberfunction decagonal(n) { // Formula for finding nth // decagonal number return 4 * n * n - 3 * n;}// Driver codelet n = 10;document.write(n + "th decagonal number : " + decagonal(n)); // This code is contributed by souravghosh0416</script> |
Output:
10th decagonal number : 370
Time Complexity: O(1)
Auxiliary Space: O(1)
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