]
qed.
-
+theorem le_exp_Sn_n_SSSO: \forall n. (exp (S n) n) \le (S(S(S O))).
+intro.
+apply (trans_le ? (sigma_p (S n) (\lambda k.true) (\lambda k.(exp n n)/k!)))
+ [apply le_exp_sigma_p_exp
+ |apply (trans_le ? (sigma_p (S n) (\lambda i.true) (\lambda i.(exp n n)/(exp (S(S O)) i))))
+ [apply le_sigma_p.intros.
+ apply le_times_to_le_div
+ [apply lt_O_exp.
+ apply lt_O_S
+ |apply (trans_le ? ((S(S O))\sup i* n \sup n/i!))
+ [apply le_times_div_div_times.
+ apply lt_O_fact
+ |apply le_times_to_le_div2
+ [apply lt_O_fact
+ |rewrite < sym_times.
+ apply le_times_r.