IOM 2020, Блиц — Задача 53

The Blitz-contest of IOM-2020

Условие

Consider the list of numbers $2$, $3$, …, $N$. All these numbers are written on a whiteboard; further, each product of two or more different numbers from this list is also written there (some numbers may appear several times). For example, for $N = 3$ we would have $2$, $3$, and $6$ on the board.

Given $N = 2021$, determine the sum of reciprocal values of all numbers written on the board (i.e., the sum of $1/x$ for all $x$ on the board).

Fractional numbers can be entered either as a decimal fraction or as $m/n$.

Отговори

Решение

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Оригинал в Архива: iom-2020-blitz-tasks.pdf · официални решения: iom-2020-blitz-answers.pdf