1999 AIME Problems/Problem 7
Problem
There is a set of 1000 switches, each of which has four positions, called 
, and 
. When the position of any switch changes, it is only from 
to 
, from to 
, from to , or from to . Initially each switch is in position . The switches are labeled with the 1000 different integers 
, where 
, and 
take on the values 
. At step i of a 1000-step process, the 
-th switch is advanced one step, and so are all the other switches whose labels divide the label on the -th switch. After step 1000 has been completed, how many switches will be in position ?
