Euler Project 29

Consider all integer combinations of a^b for 2 a 5 and 2 b 5:

2²=4, 2³=8, 2⁴=16, 2⁵=32
3²=9, 3³=27, 3⁴=81, 3⁵=243
4²=16, 4³=64, 4⁴=256, 4⁵=1024
5²=25, 5³=125, 5⁴=625, 5⁵=3125

If they are then placed in numerical order, with any repeats removed, we get the following sequence of 15 distinct terms:

4, 8, 9, 16, 25, 27, 32, 64, 81, 125, 243, 256, 625, 1024, 3125

How many distinct terms are in the sequence generated by a^b for 2 a 100 and 2 b 100?

My Solution

(defun Euler29()

(let ((numbertable (make-hash-table)))

(loop for a from 2 to 100

do(loop for b from 2 to 100

do(let ((num (expt a b)))

(if (null (gethash num numbertable))

(setf (gethash num numbertable) T)))))

(hash-table-count numbertable)))