factorial

gistfile1.clj

;; Take k-th product while n!(n-1)!...(n-k+1)!...2!1!
;;
(map (fn [x] (reduce * x)) (take 10 (iterate rest (range 10 0 -1))))
;; (3628800 362880 40320 5040 720 120 24 6 2 1)
(reduce *' (map (fn [x] (reduce *' x)) (take 10 (iterate rest (range 10 0 -1)))))
;; 6658606584104736522240000000N

gistfile2.scala

// Take k-th product while n!(n-1)!...(n-k+1)!...2!1!
//
1.to(10).reverse.toList.tails.toList.filter(_.size>0).map(_.reduce(_*_))
// res18: List[Int] = List(3628800, 362880, 40320, 5040, 720, 120, 24, 6, 2, 1)
1.to(10).reverse.toList.tails.toList.filter(_.size>0).map(_.reduce(_*_)).foldLeft(BigInt(1))(_*_)
// res19: scala.math.BigInt = 6658606584104736522240000000
10.to(1).by(-1).toList.tails.toList.filter(_.size>0).map(_.reduce(_*_)).foldLeft(BigInt(1))(_*_)
// res23: scala.math.BigInt = 6658606584104736522240000000