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本书可以伸出桌子边缘多远而不会倒塌？结果表明，
本书的最大可能悬垂距离 
（以书长为单位）是 调和级数的第 
个部分和的一半。
是一个 调和数。 前几个值是
个书长的悬垂距离所需的堆叠书本数量，求解关于 
的 
方程，并取 上限函数。对于 
, 2, ... 个书长的悬垂距离，需要 4, 31, 227, 1674, 12367, 91380, 675214, 4989191, 36865412, 272400600, ... 本书 (OEIS A014537)。