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For Alison's approach:
What happens to the numbers as you go down the rows?
What happens as you go up the rows?
For Bernard's approach:
Which numbers end in a 0 in row $A_2$?
Which numbers end in a 0 in row $A_3$?
Which of these sequences will hit 1000?
For Charlie's approach:
Can you find a similar method to Charlie's to describe the other rows?
Which descriptions include 1000?