#include <iostream> // 计算序列第 n 项的值 int calculateNthTerm(int n) { if (n == 1) { return 1; } int term = 1; for (int i = 2; i <= n; ++i) { term += (i - 2); } return term; } int main() { int n; std::cout << "请输入要计算的项数 n: "; std::cin >> n; int result = calculateNthTerm(n); std::cout << "该序列的第 " << n << " 项的值是: " << result << std::endl; return 0; }