I need some help with this induction proof.I'm like stuck at a crucial point and don't know how to get past it and complete the proof

The question says:

Suppose $\displaystyle b1,b2,b3...$

is a sequence defined as follows :$\displaystyle b1= 4 , b2 = 12 $

$\displaystyle bk = bk-1 + bk-2 $for all integers $\displaystyle k>= 3$

prove that bn is divisible by 4 for all integers n>=1

Thanks