{an}是以1为首项,1为公差的等差数列,an=n (1 2 3 4 5 6……).bn满足n-1=log2bn,即2^(n-1)=bn.{bn}是以1为首项,以2为公比的等比数列,bn=2^(n-1) (1 2 4 8 16……).求和可用错位相减法,与等比数列的推导过程相似：an=(...