C/C++ program to calculate the sum of a sequence where the nth term is n raised to the power 2 minus (n-1) raised to the power 2

Here we will see how to calculate the sum of a series with n-th term n2 - (n-1)2. The recursive relationship is as follows -

T_n = n² - (n−1)²

Therefore, The series is -

We need to find S mod (10⁹ 7) where S is the sum of all terms of the given series.

Example

#include<iostream>
#define X 1000000007
using namespace std;
long long getSum(long long n) {
   return ((n % X) * (n % X)) % X;
}
int main() {
   long long n = 56789;
   cout << getSum(n);
}

Output

224990500

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