- Trending Categories
- Data Structure
- Networking
- RDBMS
- Operating System
- Java
- iOS
- HTML
- CSS
- Android
- Python
- C Programming
- C++
- C#
- MongoDB
- MySQL
- Javascript
- PHP

- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who

In this problem, we are given an integer N. The task is to find the n-th term in series 3, 9, 21, 41, 71...

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

N = 7

169

The series is 3, 9, 21, 41, 71, 169...

A simple solution to the problem is by finding the general term of the series. The general term can be found by observing the series a bit. It is,

$$T(N) = \sum n^{2} + \sum n + 1$$

We can directly use the formula for the sum of square of first n natural numbers, first n natural number and then add the three values. At last return the resultant value,

$$T(N)=\left(\frac{n*(n+1)*(2n+1)}{6}\right)+\left(\frac{n*(n+1)}{2}\right)+1$$

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

#include <iostream> using namespace std; int findNthTerm(int n) { return ((((n)*(n + 1)*(2*n + 1)) / 6) + (n * (n + 1) / 2) + 1); } int main() { int N = 12; cout<<"The "<<N<<"th term of the series is "<<findNthTerm(N); return 0; }

The 12th term of the series is 729

- Related Questions & Answers
- Program to find N-th term of series 3 , 5 , 21 , 51 , 95 , … in C++
- C++ program to find n-th term of series 1, 3, 6, 10, 15, 21…
- Program to find N-th term of series 7, 21, 49, 91, 147, 217, …… in C++
- Program to find N-th term of series 1, 2, 11, 12, 21… in C++
- C++ program to find n-th term in the series 9, 33, 73,129 …
- Program to find N-th term of series 3, 6, 18, 24, … in C++
- Program to find N-th term of series 9, 23, 45, 75, 113… in C++
- Program to find N-th term of series 3, 5, 33, 35, 53… in C++
- Program to find N-th term of series 2, 4, 3, 4, 15… in C++
- Program to find N-th term of series 3, 12, 29, 54, 87, … in C++
- Program to find N-th term of series 0, 9, 22, 39, 60, 85, 114, 147, …in C++
- Program to find N-th term of series 3, 12, 29, 54, 86, 128, 177, 234, ….. in C++
- C++ program to find n-th term of series 2, 10, 30, 68, 130 …
- C++ program to find n-th term in the series 7, 15, 32, …
- n-th term of series 1, 17, 98, 354…… in C++

Advertisements