Find the sum of the first Nth Icosidigonal Number
Given a number N, the task is to find the sum of the first N Icosidigonal Numbers.
The first few Icosidigonal numbers are 1, 22, 63, 124, 205, 306 …
Examples:
Input: N = 3
Output: 86
Explanation:
1, 22 and 63 are the first three Icosidigonal numbers.
Input: N = 6
Output: 721
Approach:
- Initially, we need to create a function which will help us to calculate the Nth icosidigonal number.
- Now, run a loop starting from 1 to N, to find ith icosidigonal numbers.
- Add all the above calculated icosidigonal numbers.
- Finally, display the sum of the first N Icosidigonal numbers.
Below is the implementation of the above approach:
C++
// C++ program to find the sum of the // first N icosidigonal numbers #include <bits/stdc++.h> using namespace std; // Function to find the // N-th icosidigonal number int Icosidigonal_num( int n) { // Formula to calculate // nth icosidigonal number return (20 * n * n - 18 * n) / 2; } // Function to find the sum of the // first N icosidigonal number int sum_Icosidigonal_num( int n) { // Variable to store the sum int summ = 0; // Iterating in the range 1 to N for ( int i = 1; i < n + 1; i++) { // Finding the sum summ += Icosidigonal_num(i); } return summ; } // Driver code int main() { int n = 6; // Display first Nth // icosidigonal numbers cout << sum_Icosidigonal_num(n); } // This code is contributed by coder001 |
Java
// Java program to find the sum of the // first N icosidigonal numbers class GFG{ // Function to find the // N-th icosidigonal number public static int Icosidigonal_num( int n) { // Formula to calculate // nth icosidigonal number return ( 20 * n * n - 18 * n) / 2 ; } // Function to find the sum of the // first N icosidigonal number public static int sum_Icosidigonal_num( int n) { // Variable to store the sum int summ = 0 ; // Iterating in the range 1 to N for ( int i = 1 ; i < n + 1 ; i++) { // Finding the sum summ += Icosidigonal_num(i); } return summ; } // Driver code public static void main(String[] args) { int n = 6 ; // Display first Nth // icosidigonal numbers System.out.println(sum_Icosidigonal_num(n)); } } // This code is contributed by divyeshrabadiya07 |
Python3
# Python3 program to find the # sum of the first N # Icosidigonal numbers # Function to find the # N-th Icosidigonal # number def Icosidigonal_num(n): # Formula to calculate # nth Icosidigonal # number return ( 20 * n * n - 18 * n) / / 2 # Function to find the # sum of the first N # Icosidigonal number def sum_Icosidigonal_num(n) : # Variable to store # the sum summ = 0 # Iterating in the range # 1 to N for i in range ( 1 , n + 1 ): summ + = Icosidigonal_num(i) return summ # Driver code if __name__ = = '__main__' : n = 6 print (sum_Icosidigonal_num(n)) |
C#
// C# program to find the sum of the // first N icosidigonal numbers using System; class GFG{ // Function to find the // N-th icosidigonal number static int Icosidigonal_num( int n) { // Formula to calculate // nth icosidigonal number return (20 * n * n - 18 * n) / 2; } // Function to find the sum of the // first N icosidigonal number static int sum_Icosidigonal_num( int n) { // Variable to store the sum int summ = 0; // Iterating in the range 1 to N for ( int i = 1; i < n + 1; i++) { // Finding the sum summ += Icosidigonal_num(i); } return summ; } // Driver code public static void Main( string [] args) { int n = 6; // Display first Nth // icosidigonal numbers Console.WriteLine(sum_Icosidigonal_num(n)); } } // This code is contributed by AnkitRai01 |
Javascript
<script> // Javascript program to find the sum of the // first N icosidigonal numbers // Function to find the // N-th icosidigonal number function Icosidigonal_num(n) { // Formula to calculate // nth icosidigonal number return (20 * n * n - 18 * n) / 2; } // Function to find the sum of the // first N icosidigonal number function sum_Icosidigonal_num(n) { // Variable to store the sum let summ = 0; // Iterating in the range 1 to N for (let i = 1; i < n + 1; i++) { // Finding the sum summ += Icosidigonal_num(i); } return summ; } let n = 6; // Display first Nth // icosidigonal numbers document.write(sum_Icosidigonal_num(n)); // This code is contributed by divyesh072019. </script> |
Output:
721
Time complexity: O(N).
Auxiliary space: O(1) since it is using constant space for variables