Question 19Assume that $a_1\lt 2$, and for any integer $n\ge 2$, $a_n=1+a_{n-1}(a_{n-1}-1)$. If $$\frac 1{a_1}+\frac 1{a_2}+\cdots+\frac 1{a_m}=1$$ for some integer m, what is the maximum value of $16 a_1-a_{m+1}$?