A2=3A-2I +4A-4I
A3=(3A-2I)A =7A-6I +8A-8I
A4=(7A-6I)A =15A-14I +16A-16I
A5=(15A-14I)A =31A-30I
當n≥2,
An=(3-2n-2)A-(2+2n-2)I