Home  18.013A  Chapter 1  Section 1.2 


Are all such sequences countable?
Solution:
No! If you had a list of all of them, you can imagine a number that differs from every one of them because it differs from the nth in the nth decimal place. (If the nth entry on the list had 5 in the nth place give your number the value 7 in that place, otherwise give it 5.)
