P2303 [SDOI2012] Longge 的問題（歐拉函數)

P2303 [SDOI2012] Longge 的問題（歐拉函數) 傳送門html g ( n ) = ∑ i = 1 n g c d ( i , n ) = ∑ d ∣ n d × φ ( n d ) = ∑ d ∣ n n d φ ( d ) g(n)=\sum\limits_{i=1}^n gcd(i,n)=\sum_{d|n}d\times \varphi(\dfrac{n}{d})=\s

>>阅读原文<<