# Sum of all the numbers present at given level in Pascal’s triangle

Given a level L. The task is to find the sum of all the integers present at the given level in Pascal’s triangle .

A Pascal triangle with 6 levels is as shown below:

1
1 1
1 2 1
1 3 3 1
1 4 6 4 1
1 5 10 10 5 1

Examples:

Input: L = 3
Output: 4
1 + 2 + 1 = 4

Input: L = 2
Output:2

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach: If we observe carefully the series of the sum of levels will go on like 1, 2, 4, 8, 16…., which is a GP series with a = 1 and r = 2.

Therefore, sum of Lth level is L’th term in the above series.

```Lth term = 2L-1
```

Below is the implementation of the above approach:

## C++

 `// C++ implementation of the above approach ` ` `  `#include ` `using` `namespace` `std; ` ` `  `// Function to find sum of numbers at  ` `// Lth level in Pascals Triangle ` `int` `sum(``int` `h) ` `{ ` `    ``return` `pow``(2, h - 1); ` `} ` ` `  `// Driver Code ` `int` `main() ` `{ ` `    ``int` `L = 3; ` `     `  `    ``cout << sum(L); ` `     `  `    ``return` `0; ` `} `

## Java

 `// Java implementation of the approach  ` `class` `GFG ` `{ ` `     `  `    ``// Function to find sum of numbers at  ` `    ``// Lth level in Pascals Triangle  ` `    ``static` `int` `sum(``int` `h)  ` `    ``{  ` `        ``return` `(``int``)Math.pow(``2``, h - ``1``);  ` `    ``}  ` `     `  `    ``// Driver Code  ` `    ``public` `static` `void` `main (String[] args) ` `    ``{  ` `        ``int` `L = ``3``;  ` `         `  `        ``System.out.println(sum(L));  ` `    ``}  ` `} ` ` `  `// This code is contributed by AnkitRai01 `

## Python3

 `# Python3 implementation of the above approach ` ` `  `# Function to find sum of numbers at ` `# Lth level in Pascals Triangle ` `def` `summ(h): ` `    ``return` `pow``(``2``, h ``-` `1``) ` ` `  `# Driver Code ` `L ``=` `3` ` `  `print``(summ(L)) ` ` `  `# This code is contributed by mohit kumar `

## C#

 `// C# implementation of the approach  ` `using` `System; ` ` `  `class` `GFG ` `{ ` `     `  `    ``// Function to find sum of numbers at  ` `    ``// Lth level in Pascals Triangle  ` `    ``static` `int` `sum(``int` `h)  ` `    ``{  ` `        ``return` `(``int``)Math.Pow(2, h - 1);  ` `    ``}  ` `     `  `    ``// Driver Code  ` `    ``public` `static` `void` `Main () ` `    ``{  ` `        ``int` `L = 3;  ` `         `  `        ``Console.WriteLine(sum(L));  ` `    ``}  ` `} ` ` `  `// This code is contributed by anuj_67.. `

Output:

```4
```

Time Complexity: O(1)

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