你认真的吗，会杜教筛不会算复杂度
不过回答你一下，乘起来就好了 $O(k^{\frac{2}{3}}\sqrt{n})$
by __Tonycyt__ @ 2024-02-20 20:12:55
什么都想算复杂度只会害了你！
总之 $O(\text{能过})$
by Terrible @ 2024-02-20 20:13:02
$$B+\sum_{i=1}^{n/B}\sqrt{\dfrac ni}=O\left(B+\dfrac n{\sqrt B}\right)\xlongequal[]{B=n^{2/3}}O(n^{2/3})$$
by Celestial_Scarlet @ 2024-02-20 20:16:18
是我太弱了，谢谢各位大佬
by little_magicstar @ 2024-02-20 20:37:26