Вычислить сумму первых N членов ряда

#include <iostream>
#include <cmath>
 
// Function to calculate the k-th term of the series
double seriesTerm(int k, double x) {
    double sqrt_expr = std::sqrt(3); // sqrt(3) for the first term
    if (k > 1) {
        sqrt_expr = std::sqrt(4 + std::sqrt(3));
        for (int i = 2; i < k; ++i) {
            sqrt_expr = std::sqrt(3 + sqrt_expr);
        }
    }
    return (std::cos(x) + k) / sqrt_expr;
}
 
// Function to calculate the sum of the first N terms of the series
double seriesSum(int N, double x) {
    double sum = 0.0;
    for (int k = 1; k <= N; ++k) {
        sum += seriesTerm(k, x);
    }
    return sum;
}
 
int main() {
    double x;
    int N;
 
    // Input values for x and N
    std::cout << "Enter value for x: ";
    std::cin >> x;
    std::cout << "Enter value for N: ";
    std::cin >> N;
 
    // Calculate the sum of the series
    double result = seriesSum(N, x);
 
    // Output the result
    std::cout << "The sum of the first " << N << " terms of the series is: " << result << std::endl;
 
    return 0;
}

// Function to calculate the sum of the first N terms of the series
double seriesSum(int N, double x) {
   double denom = std::sqrt(3); 
   double sum = 0.0;
   for (int i = 1; i <= N; ++i) {
      sum += (std::cos(x) + i)/denom;
      denom = sqrt(3 + (i&1) + denom);
   }
   return sum;
}