LibreOJ 509. 动态几何问题 | Alpha1022's Blog

[Alpha1022]

https://www.alpha1022.me/articles/loj-509.htm

[ \begin{aligned} &\quad; \sum_{i=1}^n\sum_{j=1}^m [ij\text{ is perfect square}] \ &= \sum_{k=1}^{\min(n,m)} \mu^2(k) \left\lfloor\sqrt{\frac nk}\right\rfloor \left\lfloor\sqrt{\frac mk}\ri

[jiangruizhang]

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