b[1]=1/2
b[n+1]=3b[n]
b[2]=3b[1]=3*1/2=3/2
b[3]=3b[2]=3*3/2=9/2
b[4]=3b[3]=3*9/2=27/2
b[5]=3b[4]=3*27/2=81/2=40.5
b[1]=1/2
b[n+1]=3b[n]
b[2]=3b[1]=3*1/2=3/2
b[3]=3b[2]=3*3/2=9/2
b[4]=3b[3]=3*9/2=27/2
b[5]=3b[4]=3*27/2=81/2=40.5