# N-th term in the series 1, 11, 55, 239, 991,…in C++

C++Server Side ProgrammingProgramming

In this tutorial, we are going to write a program that finds the n-th number in the series 1, 11, 55, 239, 991...

If you clearly observe the series, you will find that the n-th number is 4n-2n-1n > 0

## Example

Let's see the code.

Live Demo

#include <bits/stdc++.h>
using namespace std;
int getNthTerm(int n) {
int num = pow(4, n) - pow(2, n) - 1;
return num;
}
int main() {
int n = 7;
cout << getNthTerm(n) << endl;
return 0;
}

## Output

If you run the above code, then you will get the following result.

16255

## Conclusion

If you have any queries in the tutorial, mention them in the comment section.

Published on 29-Jun-2021 09:31:01