Now, (n!)! is the product of the positive integers from 1 to n!.
We write the integers from 1 to n! in (n−1)! rows as follows:
1×2×3...n
(n+1)(n+2)(n+3)...(2n)
(2n+1)(2n+2)...(3n)
(3n+1)(3n+2)...(4n)
.
.
.
(n!−n+1)(n!−n+2)...(n(n−1)!)
Each of these (n−1)! rows contain n consecutive positive integers. The product of consecutive integers in each row is divisible by n! Thus, the product of all the integers from 1 to n! is divisible by (n!)(n−1)!.