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(1)
mouse moving on plane returns to origin
Source: IMOC 2017 N6
8/14/2021
A mouse walks on a plane. At time
i
i
i
, it could do nothing or turn right, then it moves
p
i
p_i
p
i
ā
meters forward, where
p
i
p_i
p
i
ā
is the
i
i
i
-th prime. Is it possible that the mouse moves back to the starting point?
number theory