#include <iostream> #include <cmath> using namespace std; int main(){ setlocale(LC_ALL, "Russian"); int n; double s = 0; cout << "N = "; cin >> n; for (int i = 1; i <= n; s += 1 / pow(2 * i + 1, 2), i++); cout << Сумма = " << s << endl; cin.get(); return 0; } или #include <iostream> #include <cmath> using namespace std; int main(){ setlocale(LC_ALL, "Russian"); int n; double s = 0; cout << "N = "; cin >> n; for (; n > 0; s += 1 / pow(2 * n + 1, 2), n--); cout << "Сумма = " << s << endl; cin.get(); return 0; }