# Sum of the series 1 / 1 + (1 + 2) / (1 * 2) + (1 + 2 + 3) / (1 * 2 * 3) + – – – – – – upto n terms.

Last Updated : 20 Feb, 2023

Given a positive integer n, find the sum of the series upto n terms.
Examples :

```Input : n = 4
Output : 3.91667
Series : (1 / 1) + (1 + 2) / (1 * 2) + (1 + 2 + 3) / (1 * 2 * 3) + (1 + 2 + 3 + 4) / (1 * 2 * 3 * 4)
= 1 / 1 + 3 / 2 + 6 / 6 + 10 / 24
= 3.91667

Input : n = 6
Output : 4.07083
Series : (1 / 1) + (1 + 2) / (1 * 2) + (1 + 2 + 3) / (1 * 2 * 3)  + (1 + 2 + 3 + 4) / (1 * 2 * 3 * 4) + (1 + 2 + 3 + 4 + 5) / (1 * 2 * 3 * 4 * 5)  + (1 + 2 + 3 + 4 + 5 + 6) / (1 * 2 * 3 * 4 * 5 * 6)
= 1 / 1 + 3 / 2 + 6 / 6 + 10 / 24 + 15 / 120 + 21 / 720
= 4.07083```

## C++

 `// CPP program to find sum of series. ` `#include ` `using` `namespace` `std; ` ` `  `double` `sumOfSeries(``int` `n) ` `{ ` `    ``double` `res = 0.0 ; ` `    ``int` `sum = 0, prod = 1; ` `    ``for` `(``int` `i = 1 ; i <= n ; i++) ` `    ``{ ` `        ``sum += i; ` `        ``prod *= i; ` `        ``res += ((``double``)sum / prod); ` `    ``} ` `    ``return` `res; ` `} ` ` `  `// Driver Code ` `int` `main() ` `{ ` `    ``int` `n = 4 ; ` `    ``cout << sumOfSeries(n) ;     ` `    ``return` `0; ` `} `

## Java

 `// Java program to find sum of series. ` `class` `GFG  ` `{ ` `static` `double` `sumOfSeries(``int` `n)  ` `{ ` `    ``double` `res = ``0.0``; ` `    ``int` `sum = ``0``, prod = ``1``; ` `    ``for` `(``int` `i = ``1``; i <= n; i++) { ` `    ``sum += i; ` `    ``prod *= i; ` `    ``res += ((``double``)sum / prod); ` `    ``} ` `    ``return` `res; ` `} ` ` `  `// Driver code ` `public` `static` `void` `main(String arg[]) { ` `    ``int` `n = ``4``; ` `    ``System.out.println(sumOfSeries(n)); ` `} ` `} ` ` `  `// This code is contributed by Anant Agarwal. `

## Python3

 `# Python program to ` `# find sum of series. ` ` `  `def` `sumOfSeries(n) : ` ` `  `    ``res ``=` `0.0` `    ``sum` `=` `0` `    ``prod ``=` `1` `    ``for` `i ``in` `range``(``1``, n ``+` `1``) : ` `     `  `        ``sum` `=` `sum` `+` `i ` `        ``prod ``=` `prod ``*` `i ` `        ``res ``=` `res ``+` `(``sum` `/` `prod) ` `         `  `    ``return` `res ` `     `  `# Driver Code ` `n ``=` `4` `print` `(``round``(sumOfSeries(n), ``5``))  ` ` `  `# This code is contributed by  ` `# Manish Shaw(manishshaw1) `

## C#

 `// C# program to find sum of series. ` `using` `System; ` ` `  `class` `GFG { ` ` `  `    ``static` `double` `sumOfSeries(``int` `n) ` `    ``{ ` `        ``double` `res = 0.0; ` `        ``int` `sum = 0, prod = 1; ` `        ``for` `(``int` `i = 1; i <= n; i++) { ` `            ``sum += i; ` `            ``prod *= i; ` `            ``res += ((``double``)sum / prod); ` `        ``} ` `        ``return` `res; ` `    ``} ` ` `  `    ``// Driver code ` `    ``public` `static` `void` `Main() ` `    ``{ ` `        ``int` `n = 4; ` `        ``Console.Write(sumOfSeries(n)); ` `    ``} ` `} ` ` `  `// This code is contributed by vt_m. `

## PHP

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## Javascript

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Output :

`3.91667`

Time complexity: O(n) since using a single loop

Auxiliary Space: O(1) for constant space for variables

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