so it cannot be a perfect square, or an even power, for this reason.
For odd powers, the following argument settles all cases: one checks the
claim for n < 9 directly; for k ≥ 9, k! is a multiple of 27, while 1! + 2! +
· · ·+8! is a multiple of 9, but not 27. Hence 1! + 2!+· · ·+n! cannot be
a cube or higher power