We used to call it a binary chop because you first test one half against the other half. Keep dividing in halves and comparing one half against the next. Think in exponents of 2. Two to the second is 4 so 4 pins requires 2+1 patterns. Two to the third is 8 so 8 pins requires 3+1 patterns. Two to the fourth is 32 so 32 pins requires 4+1.