16.已知数列{an}\{a_{n}\}{an}前nnn项和为SnS_{n}Sn,a1=1a_{1}=1a1=1,a2=2a_{2}=2a2=2,an+2−3an+1+2an=0a_{n+2}-3a_{n+1}+2a_{n}=0an+2−3an+1+2an=0,则下列正确的是((( )))