Sequences

A sequence is simply an ordered list of numbers, each following a definite rule or pattern. Instead of a random collection, every term in a sequence has a specific position — first, second, third, and so on — which we denote by $a_1, a_2, a_3, \dots$. This idea of order is what separates a sequence from a set: in a sequence, swapping two terms changes the sequence itself. Understanding how to spot the pattern and write the …