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Program to find N-th term of series 1, 3, 12, 60, 360...in C++
In this problem, we are given a number N. Our task is to create a Program to find N-th term of series 1, 3, 12, 60, 360...in C++.
Given Series
1, 3, 12, 60, 360, 2520 … N Terms
Let’s take an example to understand the problem,
Input − N = 6
Output − 2520
Solution Approach:
The general term formula for this one is a bit tricky. So, the increase in the series values is huge. So, there can be a few possibilities factorial or exponentials. So, we will first consider factorial, and on observing we can see the growth half as half of the factorial values. Also, the factorial of 2 is the first term here. So, the general formula would be,
TN = ((N+1)!)/ 2
Program to illustrate the working of our solution,
#include <iostream> using namespace std; int calcFact(int n){ if(n == 1){ return 1; } return (n*calcFact(n-1)); } int findNTerm(int N) { int nthTerm = ( (calcFact(N+1)) /2 ); return nthTerm; } int main() { int N = 8; cout<<N<<"th term of the series is "<<findNTerm(N); return 0; }
Output:
8th term of the series is 181440
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