26．（2022•徐汇区校级模拟）已知函数f(x)={(4−a)x−10,x⩽7ax−6,x>7f(x)=\left\{\begin{array}{l}({4-a})x-10,x\leqslant 7\\ {a^{x-6}},x>7\end{array}\right.f(x)={(4−a)x−10,x⩽7ax−6,x>7，数列{an}\{a_{n}\}{an}满足an=f(n)(n∈N∗)a_{n}=f(n)(n\in N^{*})an=f(n)(n∈N∗)，若数列{an}\{a_{n}\}{an}单调递增，则实数aaa的取值范围是 ___(2,4)(2,4)(2,4)___．