Question

What is the next number to follow 17, 18, 22, 31, 47, ?

Answer 1

72

Explanation:

First differences are ...

18 -17 = 1

22 -18 = 4

31 -22 = 9

47 -31 = 16

We observe that these are square numbers. The next square number is 25, so we expect the next number in sequence to be ...

47 +25 = 72