a4=8

A 1× is equal to the power of (4- 1) =8.

The equal ratio is 2.

(If I see him at ordinary times, he can immediately reflect 4× 16=64, but if you can't see it or have to write the process, forget it. )

an=2^(n- 1)

bn=3㏒2 2(n- 1)+2

=3(n- 1)+2

=3n- 1

I don't know why I have to answer this question after the college entrance examination.

Typing and talking about math problems are the most troublesome.

Adopt it.