Something

(defun fak (a)
    if (eq a 1)
    (
       1
     )else
    (
       (* a fak(- a 1 ))
    )
)
 
(fak 3)

(defun binom (n k)
    if (eq k 0)
    (
        0
    )else
    (
        if ( >= k  n)
        (
             1
        )else
        (
             (/ ( fak(n)(* fak(k) fak(n-k) )))
        )
    )
)

(binom 6 3 )