25．（2023•南海区校级模拟）函数y=x2(x>0)y=x^{2}(x>0)y=x2(x>0)的图像在点(an(a_{n}(an，an2){a}_{n}^{2})an2)处的切线与xxx轴交点的横坐标为an+1(n∈N∗)a_{n+1}(n\in N^{*})an+1(n∈N∗)，且a1=32a_{1}=32a1=32，则a2+a4+a6=a_{2}+a_{4}+a_{6}=a2+a4+a6=[ 21 ]．