(defun sqr (n)
  (* n n))

(defun sum-of-sqr-dgts (n)
  (loop for i = n then (floor i 10)
        while (plusp i)
        sum (sqr (mod i 10))))

(defun happy-p (n &optional cache)
  (or (= n 1)
      (unless (find n cache)
        (happy-p (sum-of-sqr-dgts n)
                 (cons n cache)))))

(defun happys (&aux (happys 0))
  (loop for i from 1
        while (< happys 8)
        when (happy-p i)
        collect i and do (incf happys)))

(print (happys))