(* 目的：自然数 n の階乗を求める *) 
(* sum_of_square : int -> int *) 
let rec sum_of_square n = 
  if n = 0 then 0 
           else n * n + sum_of_square (n - 1) 
 
(* テスト *) 
let test1 = sum_of_square 0 = 0 
let test2 = sum_of_square 1 = 1 
let test3 = sum_of_square 2 = 5 
let test4 = sum_of_square 3 = 14 
let test5 = sum_of_square 4 = 30