shanquan2

摘要： 答案等于$\sum_{d|(P,Q)} d\times \varphi (P/d)$设$P=\prod_{i=1}^t p_i^{m_i}$，$P=\prod_{i=1}^t p_i^{k_i}$答案就等于$P=\prod p_i^{m_i-1}\times((k_i+1)(p_i-1)+[k_i= 阅读全文