A pattern, or sequence, is a set of numbers that are connected in some way. And the numbers in the sequence are called terms. All sequences have a rule. The numbers could count on by three each time, ...

1, 11, 21, 1211, 111221. These are the first five elements of a number sequence. Can you figure out what comes next? If you're trying a bunch of arithmetic operations to make the numbers work, you're ...