Question

已知数列{a}满足a1=1,a1乘以a2乘以a3.乘以。。。an=n*2(n大于等于2),则a2+a4的值

Answer 1

如果你的题目是a1*a2*a3·····=n^2(n的2次方)
a1=1
a2=2*2=4
a2*a3=3*3=9
a3=9/4
a2*a3*a4=4*4=16
a4=16/9
a2+a4=4+16/9=52/9

如果是a1*a2*a3····an=2*n(n的两倍)
a1=1
a2=4
a1*a2*a3=4*a3=2*3=6
a3=6/4=3/2
a1*a2*a3*a4=2*4=8
a4=8/6=4/3
a2+a4=4+4/3=16/3

Answer 2

a1a2=2*2
a2=
a1a2a3=3*2
a3=
a1a2a3a4=4*2
a4=
a2+a4=