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# C++ program to find n-th term in the series 7, 15, 32, â€¦

In this problem, we are given an integer N. The task is to find n-th term in series 7, 15, 32....

**Let’s take an example to understand the problem,**

## Input

N = 6

## Output

281

## Explanation

The series upto nth term is 7, 15, 32, 67, 138, 281

## Solution Approach

The solution to the problem lies in decoding the series. You can see the series is a mix of series.

The subtracting the values,

T(2) - T(1) = 15 - 7 = 8 T(3) - T(2) = 32 - 15 = 17 So, T(2) = 2*T(1) + 1 T(3) = 2*T(2) + 2 T(n) = 2*T(n-1) + (n-1)

So, the value of the nth term is found using the last term. To find these we will loop from 1 to n and find each value of the series.

**Program to illustrate the working of our solution,**

## Example

#include <iostream> using namespace std; int findNthTerm(int n) { if (n == 1) return 7; int termN = 7; for (int i = 2; i <= n; i++) termN = 2*termN + (i - 1); return termN; } int main(){ int n = 12; cout<<"The series is 7, 15, 32, 67...\n"; cout<<n<<"th term of the series is "<<findNthTerm(n); return 0; }

## Output

The series is 7, 15, 32, 67... 12th term of the series is 18419

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