The next number in this sequence is 24. This would follow the pattern of adding five to a number and then subtracting two. The first three numbers of this sequence indicate this: 13 + 5 = 18 and 18 - 2 = 16.
Recognizing a pattern within a sequence of numbers helps determine numbers that occur much later, often without writing down the entire sequence. Being able to recognize a pattern has additional applications, such as determining probability. There are some number sequences so common, they have a name. One example is the Fibonacci sequence, in which a number is the sum of the two previous numbers before it.