Theorem harcl

Description: Values of the Hartogs function are ordinals (closure of the Hartogs function in the ordinals). (Contributed by Stefan O'Rear, 11-Feb-2015)

	Ref	Expression
Assertion	harcl	|- ( har ` X ) e. On

Proof

Step	Hyp	Ref	Expression
1		harf	|- har : _V --> On
2		0elon	|- (/) e. On
3	1 2	f0cli	|- ( har ` X ) e. On