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Chisinau MO p1 1949-56 VIII-IX crossing every 15th no from 1-100 in a circle

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March 15, 2021
algebra

Problem Statement

The numbers 1,2,...,10001, 2, ..., 1000 are written out in a row along a circle. Starting from the first, every fifteenth number in the circle is crossed out (1,16,31,...)(1, 16, 31, ...), in this case, the crossed out numbers are still taken into account at each new round of the circle. How many numbers are left uncrossed?
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