# Enneacontagon Number

• Last Updated : 22 Jun, 2021

Given a number N, the task is to find Nth Enneacontagon number.

A Enneacontagon number. is class of figurate number. It has 90 – sided polygon called enneacontagon. The N-th enneacontagon number countâ€™s the 90 number of dots and all others dots are surrounding with a common sharing corner and make a pattern. The first few enneacontagonol numbers are 1, 90, 267, 532 …

Examples:

Input: N = 2
Output: 90
Explanation:
The second enneacontagonol number is 90.
Input: N = 3
Output: 267

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

• Nth term of s sided polygon =

• Therefore Nth term of 90 sided polygon is

•

Below is the implementation of the above approach:

## C++

 // C++ program for above approach#include using namespace std; // Finding the nth enneacontagon Numberint enneacontagonNum(int n){    return (88 * n * n - 86 * n) / 2;} // Driver Codeint main(){    int n = 3;    cout << "3rd enneacontagon Number is = "         << enneacontagonNum(n);     return 0;} // This code is contributed by Akanksha_Rai

## C

 // C program for above approach#include #include  // Finding the nth enneacontagon Numberint enneacontagonNum(int n){    return (88 * n * n - 86 * n) / 2;} // Driver program to test above functionint main(){    int n = 3;    printf("3rd enneacontagon Number is = %d",           enneacontagonNum(n));     return 0;}

## Java

 // Java program for above approachclass GFG{ // Finding the nth enneacontagon numberpublic static int enneacontagonNum(int n){    return (88 * n * n - 86 * n) / 2;} // Driver code   public static void main(String[] args){    int n = 3;     System.out.println("3rd enneacontagon Number is = " +                                    enneacontagonNum(n));}} // This code is contributed by divyeshrabadiya07

## Python3

 # Python3 program for above approach # Finding the nth enneacontagon Numberdef enneacontagonNum(n):     return (88 * n * n - 86 * n) // 2 # Driver Coden = 3print("3rd enneacontagon Number is = ",                   enneacontagonNum(n)) # This code is contributed by divyamohan123

## C#

 // C# program for above approachusing System;class GFG{ // Finding the nth enneacontagon numberpublic static int enneacontagonNum(int n){    return (88 * n * n - 86 * n) / 2;} // Driver codepublic static void Main(String[] args){    int n = 3;     Console.WriteLine("3rd enneacontagon Number is = " +                                   enneacontagonNum(n));}} // This code is contributed by Rajput-Ji

## Javascript

 
Output:
3rd enneacontagon Number is = 267

Time Complexity: O(1)

Auxiliary Space: O(1)

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