Task

The objective is to write a function that finds the sum of all positive multiples of 3 or 5 below n.

Show output for n = 1000.

This is is the same as Project Euler problem 1.

Extra credit: do this efficiently for n = 1e20 or higher.




(defun sum-3-5-slow (limit)
  (loop for x below limit
        when (or (zerop (rem x 3)) (zerop (rem x 5)))
          sum x))