标签：lfloor frac 分块 数论 sum rfloor
参考
\[\Large\sum_{i=1}^{n}\lfloor\frac{n}{i}\rfloor=2\sum_{i=1}^{\lfloor\sqrt{n}\rfloor}\lfloor{\frac{n}{i}\rfloor-\lfloor\sqrt{n}\rfloor^2}
\]
标签：lfloor,
frac,
分块,
数论,
sum,
rfloor
From： https://www.cnblogs.com/zxyc/p/16831271.html