Сократите дробь :

n! / 2!*(n - 2)!

 

(4m-1)! / (4m-3)!

n! / 2!*(n - 2)!  =(n - 2)! (n-1) n / 1*2*(n - 2)! = (n^2- n) / 2

(4m-1)! / (4m-3)!  = (4m-3)! (4m-2) (4m-1) / (4m-3)! = (4m-2) (4m-1) = 16m^2 -12m +2