" 
 :::::::Ah, there is the source of your confusion.  In actuality, you aren't given any information about having the first or second half of the sequence.  If you were, then you'd be right.  But read the question above: ""is there at least one head"".  That is exactly why it's paradoxical: intuition is used to one-then-the-other type reasoning, but here it doesn't apply, so intuition is wrong.    "