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【Luogu3768】简单的数学题（莫比乌斯反演，杜教筛） 题面 "洛谷" $$求\sum_{i=1}^n\sum_{j=1}^nijgcd(i,j)$$ $ n include include include include include include include include incl 阅读全文
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【BZOJ4916】神犇和蒟蒻（杜教筛） 题面 "BZOJ" 求 $$\sum_{i=1}^n\mu(i^2)\ \ 和\ \sum_{i=1}^n\varphi(i^2)$$ 其中$$n include include include include include include include 阅读全文
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【BZOJ3944】Sum（杜教筛） 题面 求$$\sum_{i=1}^n\mu(i)和\sum_{i=1}^n\phi(i)$$ 范围：$n include include include include include include include include include using 阅读全文