a function to handle numbers this way

Question

Hi, 

 

I have a series of numbers This series takes values (A) and (B) by dividing by 2

for Example

The number (6) and its multipliers

 represent two values A and B .

The first group .

Numbers from 1: 3 take the value A .

Numbers from 4: 6 take the value B .

 

The Second group .

Numbers from 7: 9 take the value A .

Numbers from 10: 12 take the value B .

 

I want a function that returns the value to either A or B .