A:920 kJ
B:557 kJ
C:436 kJ
D:188 kJ
心脏的四个腔中,壁最厚的是( )
(Ⅰ)求证:数列logman=2n+2,{an}是等比数列;
(Ⅱ)若bn=anf(an),记数列{bn}的前n项和为Sn,当m= 2 时,求Sn.