1 bn-cn = an(q- 1)-a & lt； n+2 & gt； (q- 1)=(q- 1)(an-a & lt； n+2 & gt； Because an is an equal proportion of positive integers, q must be greater than 1 and an is a monotonically increasing function, BN-CN

2

|b|*ab/|a||b|=n|a|

n=ab/|a|2

choose one