EarringYYR

2021.2.6  AFO

  https://www.cnblogs.com/cjyyb/p/9479258.html O(nlogn)-O(1)求k级祖先： https://zhuanlan.zhihu.com/p/25984772

$$ \prod_{i = 1}(1 - x^i) = \sum_{i = 0} (-1)^i x^{i * (3 * i \pm 1) \over 2} $$