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C++ program to find Nth number of the series 1, 6, 15, 28, 45, …..
In this problem, we are given an integer value N. Our task is to create a program to Find Nth number of the series 1, 6, 15, 28, 45, …
In the series, every element is 2 less than the mean of the previous and next element.
Let’s take an example to understand the problem,
Input
N = 5
Output
45
Solution Approach
The Nth term of the series 1, 6, 15, 28, 45, … can be found using the formula,
TN = 2*N*N - N
Program to illustrate the working of our solution,
Example
#include <iostream>
using namespace std;
#define mod 1000000009
int calcNthTerm(long n) {
return (((2 * n * n) % mod) - n + mod) % mod;
}
int main(){
long N = 19;
cout<<N<<"th Term of the series is "<<calcNthTerm(N);
return 0;
}Output
19th Term of the series is 703
Updated on: 13-Mar-2021
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