Program to find N-th term of series 7, 21, 49, 91, 147, 217, …… in C++

In this problem, we are given a number n that denotes the nth term of the series. Our task is to create a program to find the N-th term of series 7, 21, 49, 91, 147, 217, …… in C++.Problem Description - We will find the nth term of the series 7, 21, 49, 91, 147, 217, … and for that, we will deduce the general term of the series.Let’s take an example to understand the problem,Input − N = 5Output − 147<h2>Solution Approach:</h2>Let’s deduce the general term of the given series. The series is −<pre class="result notranslate">7, 21, 49, 91, 147, 217, …</pre>We can see that 7 is common here,<pre class="result notranslate">7 * (1, 3, 7, 13, 21, 31, ...)</pre>Here, we can observe that this series is increasing like a square series. So,<pre class="result notranslate">Series: 7 * (12 , (22 - 1), (33 - 2), (42 - 3), (52 - 4), (62 - 5), ....)</pre>The general term of the series can be generalized as −<pre class="result notranslate">Tn = 7*(n2 - (n-1))</pre>Using the general term formula, we can find any value of the series.For example,<pre class="result notranslate">T4 = 7*((4^2) - (4-1)) = 7(16 - 3) = 91 T7 = 7*((7^2) - (7-1)) = 7(49 - 6) = 301</pre><h2>Example</h2><a class="demo" href="http://tpcg.io/WJbX9C0k" rel="nofollow" target="_blank"> Live Demo</a><pre class="prettyprint notranslate">#include <iostream> using namespace std; int findNTerm(int N) {    int nthTerm = ( 7*((N*N) - (N - 1)) );    return nthTerm; } int main() {    int N = 9;    cout<<N<<"th term of the series is "<<findNTerm(N);    return 0; }</pre><h2>Output:</h2><pre class="result notranslate">9th term of the series is 511</pre>

Ayush Gupta

Updated on 01-Oct-2020 11:35:06

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