In which columns do the square numbers appear?
In which columns do the squares of even numbers appear? Can
you explain why?
And the squares of odd numbers? Can you explain why?
How can we describe the numbers in a particular column?
You might want to start by looking at the completely empty
columns.
a) A four digit number (in base 10) aabb is a perfect square. Discuss ways of systematically finding this number.
(b) Prove that 11^{10}-1 is divisible by 100.