(loop
     with arr = (make-array (1+ maxi)
                              :element-type 'bit
                              :initial-element 0)
     for numb from 2 to (isqrt maxi)
     when (zerop (bit arr numb))
     collect numb
     and do (loop for composite from (expt numb 2)
               to maxi by numb
               do (setf (bit arr composite) 1))))