Example: Sum of First N Even Numbers (Formula-based) in C++

C
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Java
Python
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// Sum of First N Even Numbers (Formula-based)
#include <iostream>
using namespace std;

int main() {
    // Step 1: Define the number of terms
    int N = 5; // Example: Sum of the first 5 even numbers

    // Step 2: Calculate the first and last terms
    int firstTerm = 2;
    int lastTerm = 2 * N;

    // Step 3: Apply the arithmetic series sum formula
    // Using long long for sum to handle potentially large results
    long long sum = (long long)N / 2 * (firstTerm + lastTerm);

    // Step 4: Print the final sum
    cout << "Calculating sum of first " << N << " even numbers using formula:" << endl;
    cout << "The sum is: " << sum << endl;

    return 0;
}