4. 设数列{an}\{a_{n}\}{an}为等比数列,若a2+a3+a4=2a_{2}+a_{3}+a_{4}=2a2+a3+a4=2,a3+a4+a5=4a_{3}+a_{4}+a_{5}=4a3+a4+a5=4,则数列{an}\{a_{n}\}{an}的前6项和为((( )))