To the readers, now too numerous to respond to individually, who think I should have counted B-Tu B-Tu twice:

(1) On that logic, there are six possibilities on a two-coin toss: TT (twice), TH, HT, and HH (twice). The possibility of getting two heads on a two-coin toss is therefore, according to you, 1/3. Do you believe this?

(2) Please explain my empirical result, or point to an error in my code.