The sequence represents the cube of integers starting at 1 and increasing by 1 at each step. 13 = 1 : 23 = 8 : 33 = 27 : 43 = 64 : then next two numbers are 53 = 125 : 63 = 216

There are only a handful of numbers in the range [1,100] that are perfect cubes of whole numbers. These are: 1 (13) 8 (23) 27 (33) and 64 (43) The next highest would be 53, which is 125, greater than 100.

Four of them: 1, 8, 27 & 64. Including negative numbers which are all less than 125, there are infinitely many as they also include: -1, -8, -27, -64, -125, -216, ...