S0=[ABR][ACA][DAB][RA]
is not S[0]S[3]S[6]S[9]
. S[0]S[3]S[6]S[9]
would be AADR
.
This is what happens:
For i=0
:
<S[3i]S[3i+1]S[3i+2]> = <S[3*0]S[3*0+1]S[3*0+2]> = <S[0]S[1]S[2]> = <ABR>
For i=1
:
<S[3i]S[3i+1]S[3i+2]> = <S[3*1]S[3*1+1]S[3*1+2]> = <S[3]S[4]S[5]> = <ACA>
For i=2
:
<S[3i]S[3i+1]S[3i+2]> = <S[3*2]S[3*2+1]S[3*2+2]> = <S[6]S[7]S[8]> = <DAB>
For i=3
:
<S[3i]S[3i+1]S[3i+2]> = <S[3*3]S[3*3+1]S[3*3+2]> = <S[9]S[10]S[11]> = <RA >