Program to find the sum of the series (1/a + 2/a^2 + 3/a^3 + … + n/a^n)
Given two integers 
and 
. The task is to find the sum of the series 1/a + 2/a2 + 3/a3 + … + n/an.
Examples:
Input: a = 3, n = 3
Output: 0.6666667
The series is 1/3 + 1/9 + 1/27 which is
equal to 0.6666667
Input: a = 5, n = 4
Output: 0.31039998
Approach: Run a loop from 1 to n and get the 
term of the series by calculating term = (i / ai). Sum all the generated terms which is the final answer.
Below is the implementation of the above approach:
C++
// C++ program to find the sum of // the given series #include <stdio.h>#include <math.h> #include <iostream>using namespace std;// Function to return the // sum of the series float getSum(int a, int n) { // variable to store the answer float sum = 0; for (int i = 1; i <= n; ++i) { // Math.pow(x, y) returns x^y sum += (i / pow(a, i)); } return sum; } // Driver code int main() { int a = 3, n = 3; // Print the sum of the series cout << (getSum(a, n)); return 0;}// This code is contributed // by Sach_Code |
Java
// Java program to find the sum of the given seriesimport java.util.Scanner;public class HelloWorld { // Function to return the sum of the series public static float getSum(int a, int n) { // variable to store the answer float sum = 0; for (int i = 1; i <= n; ++i) { // Math.pow(x, y) returns x^y sum += (i / Math.pow(a, i)); } return sum; } // Driver code public static void main(String[] args) { int a = 3, n = 3; // Print the sum of the series System.out.println(getSum(a, n)); }} |
Python 3
# Python 3 program to find the sum of # the given series import math# Function to return the # sum of the series def getSum(a, n): # variable to store the answer sum = 0; for i in range (1, n + 1): # Math.pow(x, y) returns x^y sum += (i / math.pow(a, i)); return sum; # Driver code a = 3; n = 3; # Print the sum of the series print(getSum(a, n)); # This code is contributed # by Akanksha Rai |
C#
// C# program to find the sum // of the given seriesusing System;class GFG{ // Function to return the sum// of the seriespublic static double getSum(int a, int n){ // variable to store the answer double sum = 0; for (int i = 1; i <= n; ++i) { // Math.pow(x, y) returns x^y sum += (i / Math.Pow(a, i)); } return sum;}// Driver codestatic public void Main (){ int a = 3, n = 3; // Print the sum of the series Console.WriteLine(getSum(a, n));}}// This code is contributed by jit_t |
PHP
<?php// PHP program to find the// sum of the given series// Function to return the // sum of the seriesfunction getSum($a, $n){ // variable to store the answer $sum = 0; for ($i = 1; $i <= $n; ++$i) { // Math.pow(x, y) returns x^y $sum += ($i / pow($a, $i)); } return $sum;}// Driver code$a = 3;$n = 3;// Print the sum of the seriesecho (getSum($a, $n));// This code is contributed by akt_mit?> |
Javascript
<script>// Javascript program to find the sum of the given series // Function to return the sum of the series function getSum( a, n) { // variable to store the answer let sum = 0; for (let i = 1; i <= n; ++i) { // Math.pow(x, y) returns x^y sum += (i / Math.pow(a, i)); } return sum; } // Driver code let a = 3, n = 3; // Print the sum of the series document.write(getSum(a, n).toFixed(7));// This code contributed by Princi Singh </script> |
Output:
0.6666667
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