Mathematics

• Coupon collector's problem
• 赠券收集问题
• 调和数, Euler–Mascheroni constant
• 估算公式:<math>

\operatorname{E}(T) = n \cdot H_n = n \log n + \gamma n + \frac1{2} + o(1), \ \ \text{as} \ n \to \infty, </math> where <math>\gamma \approx 0.5772156649</math> is the Euler–Mascheroni constant.