已知{an}\{a_n\}{an}是等差数列，{bn}\{b_n\}{bn}是等比数列，an=2n+1a_n = 2n+1an=2n+1，bn=2nb_n = 2^nbn=2n，求sum{k=1}{n}ak∗bksum_\{k=1\}^\{n\} a_k*b_ksum{k=1}{n}ak∗bk。