If 3=18, 4=32, 5=50, 6=72, 7...

A man walks into the Friars barbershop, sits down in the chair and the barber asks, “How do you want your haircut?”
The man says, ” I would like the sideburns one high and one low, a few long hairs sticking out of the back and a few chunks on the side and top.”
The barber looks puzzled and says, “I’m not sure I can do that.”
The customer says, “Why not, you did it that way last time.”