A computer program generates a sequence of numbers a1, a2, a3,... such that a1=1, a2=2, and ak = a(k-1) + 3ak-2 for 2 < k < n for n=20. Find a5.	Choices
A) 10  B) 24  C) 28  D) 32  E) 38
a1=1   a2=2   a3=3*2-2= 
<gadget id="calculator">3*2-2</gadget>
<output>4</output>
4   a4=3*4-2= 
<gadget id="calculator">3*4-2</gadget>
<output>10</output>
10   a5=3*10-2= 
<gadget id="calculator">3*10-2</gadget>
<output>28</output>
28   28
<result>C</result>
A computer program generates a sequence of numbers a1, a2, a3,... such that a1=1, a2=2, and ak = a(k-1) + 3ak-2 for 2 < k < n for n=20. Find a5.