Not true. nn ≤ n!2 for all n a natural number.

Proof:

nn = n * n * n * ... * n * n * n
n! = n * (n-1) * (n-2) * ... * 3 * 2 * 1
n! = 1 * 2 * 3 * ... * (n-2) * (n-1) * n
=> n!2 = (n*1) * ((n-1)*2) * ((n-2)*3) * ... * (3*(n-2)) * (2*(n-1)) * (1*n)

This sequence contains n terms and each term is of the form ((n-i)*(i+1))
(n-i)*(i+1) = ni - i2 + n - i
This is obviously greater than or equal to n for all i such that 1 ≤ i ≤ n
Hence, the sequence is the product of n terms, all greater than n. Hence it is greater than or equal to nn.

QED


Jurph: Fixed. Now it says ≤ all the way through, rather than <. Stupid typos.