一、选择题
1.(2013· 梅州模拟)已知数列{an}是公差为2的等差数列,且a1,a2,a5成等比数列,则{an}的前5项和S5= ( )
A.20 B.30 C.25 D.40
2.数列{an}的前n项和为Sn,若a1=1,an+1=3Sn(n≥1),则a6=( )
A.3×44 B.3×44+1
C.44 D.44+1
3.已知数列{an}满足a1=1,an+1=则其前6项之和是( )
A.16 B.20 C.33 D.120
4.在数列{an}中,a1=2,an+1=an+ln,则an=( )
A.2+lnn B.2+(n-1)lnn
C.2+nlnn D.1+n+lnn
