一道类似于数列收敛的数学题

Kempner seriesKempner\u0026#39;s proof of convergence is simple and is repeated in many textbooks. We group the terms of the sum by the number of digits in the denominator. The number of n-digit positive integers that have no 9 digits is exactly 【一道类似于数列收敛的数学题】 一道类似于数列收敛的数学题
and each is bigger than or equal to 一道类似于数列收敛的数学题
so the contribution of this group to the sum is less than 一道类似于数列收敛的数学题
. Therefore the whole sum is bounded by 80.
The same argument works for any omitted digit.
谁这么坑让你证明它大于80的?


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