Tie random ends: How many loops?
3Blue1Brown376 字 (约 2 分钟)
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Tie 100 ends of 50 strings randomly in pairs until no ends remain; the expected number of loops is the 50th odd harmonic number ≈ 4.5.
入选理由:期望环数为第n个调和数Hₙ = 1 + 1/2 + ... + 1/n,当n=50时H₅₀≈4.499。
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